Encoder, decoder, encoding method, decoding method, and recording medium

ABSTRACT

An encoder partitions into blocks using a set of block partition modes. The set of block partition modes includes a first partition mode for partitioning a first block, and a second block partition mode for partitioning a second block which is one of blocks obtained after the first block is partitioned. When the number of partitions of the first block partition mode is three, the second block is a center block among the blocks obtained after partitioning the first block, and the partition direction of the second block partition mode is same as the partition direction of the first block partition mode, the second block partition mode indicates that the number of partitions is only three. A parameter for identifying the second block partition mode includes a first flag indicating a horizontal or vertical partition direction, and does not include a second flag indicating the number of partitions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. continuation application of U.S. patentapplication Ser. No. 17/306,483 filed on May 3, 2021, which is a U.S.continuation application of U.S. patent application Ser. No. 17/087,128filed on Nov. 2, 2020, which is a U.S. continuation application of PCTInternational Patent Application Number PCT/JP2019/018650 filed on May9, 2019, claiming the benefit of priority of U.S. Provisional PatentApplication No. 62/674,812 filed on May 22, 2018 and Japanese PatentApplication Number 2019-028523 filed on Feb. 20, 2019, the entirecontents of which are hereby incorporated by reference.

BACKGROUND 1. Technical Field

The present disclosure relates to methods and apparatuses for encodingand decoding video and images using block partition.

2. Description of the Related Art

In conventional image and video encoding methods, an image is typicallypartitioned into blocks and encoding and decoding processes areperformed at block level. In recent video standards development, theencoding and decoding processes can be performed at various block sizesother than typical 8×8 or 16×16 sizes. In an image, a range of sizesfrom 4×4 to 256×256 can be used for encoding and decoding processes ofan image.

SUMMARY

An encoder according to an aspect of the present disclosure is anencoder that encodes a picture and includes: a processor; and memory,wherein the processor includes: a block partition determiner thatpartitions the picture into a plurality of blocks, using a set of blockpartition modes obtained by combining one or more block partition modeseach of which defines a partition type, the picture being read from thememory; and an encoding unit that encodes the plurality of blocks, theset of block partition modes includes a first partition mode thatdefines a partition direction and a total number of partitions forpartitioning a first block, and a second block partition mode thatdefines a partition direction and a total number of partitions forpartitioning a second block which is one of blocks obtained after thefirst block is partitioned, when the total number of partitions of thefirst block partition mode is three, the second block is a center blockamong the blocks obtained after the first block is partitioned, and thepartition direction of the second block partition mode is same as thepartition direction of the first block partition mode, the second blockpartition mode includes only a block partition mode indicating that thetotal number of partitions is three, and a parameter for identifying thesecond block partition mode includes a first flag indicating whether ablock is to be partitioned horizontally or vertically, and does notinclude a second flag indicating a total number of partitions into whichthe block is to be partitioned.

A decoder according to an aspect of the present disclosure is a decoderthat decodes an encoded signal and includes: a processor; and memory,wherein the processor includes: a block partition determiner thatpartitions the encoded signal into a plurality of blocks, using a set ofblock partition modes obtained by combining one or more block partitionmodes each of which defines a partition type, the encoded signal beingread from the memory; and a decoding unit that decodes the plurality ofblocks, the set of block partition modes includes a first partition modethat defines a partition direction and a total number of partitions forpartitioning a first block, and a second block partition mode thatdefines a partition direction and a total number of partitions forpartitioning a second block which is one of blocks obtained after thefirst block is partitioned, when the total number of partitions of thefirst block partition mode is three, the second block is a center blockamong the blocks obtained after the first block is partitioned, and thepartition direction of the second block partition mode is same as thepartition direction of the first block partition mode, the second blockpartition mode includes only a block partition mode indicating that thetotal number of partitions is three, and a parameter for identifying thesecond block partition mode includes a first flag indicating whether ablock is to be partitioned horizontally or vertically, and does notinclude a second flag indicating a total number of partitions into whichthe block is to be partitioned.

It should be noted that general and specific aspects described above maybe implemented using a system, a method, an integrated circuit, acomputer program, or a computer-readable recording medium such as aCD-ROM, or any arbitrary combination of systems, methods, integratedcircuits, computer programs, or computer-readable recording media.

BRIEF DESCRIPTION OF DRAWINGS

These and other objects, advantages and features of the disclosure willbecome apparent from the following description thereof taken inconjunction with the accompanying drawings that illustrate a specificembodiment of the present disclosure.

FIG. 1 is a block diagram illustrating a functional configuration of theencoder according to Embodiment 1;

FIG. 2 illustrates one example of block splitting according toEmbodiment 1;

FIG. 3 is a chart indicating transform basis functions for eachtransform type;

FIG. 4A illustrates one example of a filter shape used in ALF;

FIG. 4B illustrates another example of a filter shape used in ALF;

FIG. 4C illustrates another example of a filter shape used in ALF;

FIG. 5A illustrates 67 intra prediction modes used in intra prediction;

FIG. 5B is a flow chart for illustrating an outline of a predictionimage correction process performed via OBMC processing;

FIG. 5C is a conceptual diagram for illustrating an outline of aprediction image correction process performed via OBMC processing;

FIG. 5D illustrates one example of FRUC;

FIG. 6 is for illustrating pattern matching (bilateral matching) betweentwo blocks along a motion trajectory;

FIG. 7 is for illustrating pattern matching (template matching) betweena template in the current picture and a block in a reference picture;

FIG. 8 is for illustrating a model assuming uniform linear motion;

FIG. 9A is for illustrating deriving a motion vector of each sub-blockbased on motion vectors of neighboring blocks;

FIG. 9B is for illustrating an outline of a process for deriving amotion vector via merge mode;

FIG. 9C is a conceptual diagram for illustrating an outline of DMVRprocessing;

FIG. 9D is for illustrating an outline of a prediction image generationmethod using a luminance correction process performed via LICprocessing;

FIG. 10 is a block diagram illustrating a functional configuration ofthe decoding device according to Embodiment 1;

FIG. 11 is a flow chart of a video encoding process according toEmbodiment 2;

FIG. 12 is a flow chart of a video decoding process according toEmbodiment 2;

FIG. 13 is a flow chart of a video encoding process according toEmbodiment 3;

FIG. 14 is a flow chart of a video decoding process according toEmbodiment 3;

FIG. 15 is a block diagram illustrating the structure of a video/imageencoder according to Embodiment 2 or 3;

FIG. 16 is a block diagram illustrating the structure of a video/imagedecoder according to Embodiment 2 or 3;

FIG. 17 illustrates examples of possible locations of a first parameterin a compressed video bitstream according to Embodiment 2 or 3;

FIG. 18 illustrates examples of possible locations of a second parameterin a compressed video bitstream according to Embodiment 2 or 3;

FIG. 19 illustrates an example of a second parameter following after afirst parameter according to Embodiment 2 or 3;

FIG. 20 illustrates an example in which a second partition mode is notselected for partitioning a 2N pixels by N pixels block, as illustratedin step (2c), in Embodiment 2;

FIG. 21 illustrates an example in which a second partition mode is notselected for partitioning a N pixels by 2N pixels block, as illustratedin step (2c), in Embodiment 2;

FIG. 22 illustrates an example in which a second partition mode is notselected for partitioning a N pixels by N pixels block, as illustratedin step (2c), in Embodiment 2;

FIG. 23 illustrates an example in which a second partition mode is notselected for partitioning a N pixels by N pixels block, as illustratedin step (2c), in Embodiment 2;

FIG. 24 illustrates an example of partitioning a 2N pixels by N pixelsblock using a partition mode selected when the second partition mode isnot to be selected, as illustrated in step (3), in Embodiment 2;

FIG. 25 illustrates an example of partitioning a N pixels by 2N pixelsblock using a partition mode selected when the second partition mode isnot to be selected, as illustrated in step (3), in Embodiment 2;

FIG. 26 illustrates an example of partitioning a N pixels by N pixelsblock using a partition mode selected when the second partition mode isnot to be selected, as illustrated in step (3), in Embodiment 2;

FIG. 27 illustrates an example of partitioning a N pixels by N pixelsblock using a partition mode selected when the second partition mode isnot to be selected, as illustrated in step (3), in Embodiment 2;

FIG. 28 illustrates examples of partition modes for partitioning a Npixels by N pixels block in Embodiment 2. (a) to (h) show differentpartition modes;

FIG. 29 illustrates examples of partition types and partition directionsfor partitioning a N pixels by N pixels block in Embodiment 3. (1), (2),(3), and (4) are different partition types, (1 a), (2 a), (3 a), and (4a) are different partition modes from related partition types invertical partition direction, and (1 b), (2 b), (3 b), and (4 b) aredifferent partition modes from related partition types in horizontalpartition direction;

FIG. 30 illustrates an advantage of encoding partition type beforepartition direction as compared to encoding partition direction beforepartition type, according to Embodiment 3;

FIG. 31A illustrates an example of splitting a block into sub blocksusing a set of partition modes with fewer bins in encoding partitionmodes;

FIG. 31B illustrates an example of splitting a block into sub blocksusing a set of partition modes with fewer bins in encoding partitionmodes;

FIG. 32A illustrates an example of splitting a block into sub blocksusing a set of partition modes that appears first in a predeterminedorder of a plurality of sets of partition modes;

FIG. 32B illustrates an example of splitting a block into sub blocksusing a set of partition modes that appears first in a predeterminedorder of a plurality of sets of partition modes;

FIG. 32C illustrates an example of splitting a block into sub blocksusing a set of partition modes that appears first in a predeterminedorder of a plurality of sets of partition modes;

FIG. 33 illustrates an overall configuration of a content providingsystem for implementing a content distribution service;

FIG. 34 illustrates one example of encoding structure in scalableencoding;

FIG. 35 illustrates one example of encoding structure in scalableencoding;

FIG. 36 illustrates an example of a display screen of a web page;

FIG. 37 illustrates an example of a display screen of a web page;

FIG. 38 illustrates one example of a smartphone;

FIG. 39 is a block diagram illustrating a configuration example of asmartphone;

FIG. 40 is a diagram illustrating an example of a restriction on apartition mode for splitting a rectangular block into three sub blocks;

FIG. 41 is a diagram illustrating an example of a restriction on apartition mode for splitting a block into two sub blocks;

FIG. 42 is a diagram illustrating an example of a restriction on apartition mode for splitting a square block into three sub blocks;

FIG. 43 is a diagram illustrating an example of a restriction on apartition mode for splitting a rectangular block into two sub blocks;

FIG. 44 is a diagram illustrating an example of a restriction based onthe partition direction of a partition mode for splitting anon-rectangular block into two sub blocks; and

FIG. 45 is a diagram illustrating an example of a valid partitiondirection of a partition mode for splitting a non-rectangular block intotwo sub blocks.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments will be described in detail with reference tothe drawings.

Note that each of the embodiments described below shows a general orspecific example. The numerical values, shapes, materials, components,the arrangement and connection of the components, steps, order of thesteps, etc., indicated in the following embodiments are mere examples,and therefore are not intended to limit the scope of the claims.Furthermore, among the components in the following embodiments, thosenot recited in any one of the independent claims defining the broadestinventive concepts are described as optional components.

Embodiment 1

First, an outline of Embodiment 1 will be presented as one example of anencoder and a decoder to which the processes and/or configurationspresented in subsequent description of aspects of the present disclosureare applicable. Note that Embodiment 1 is merely one example of anencoder and a decoder to which the processes and/or configurationspresented in the description of aspects of the present disclosure areapplicable. The processes and/or configurations presented in thedescription of aspects of the present disclosure can also be implementedin an encoder and a decoder different from those according to Embodiment1.

When the processes and/or configurations presented in the description ofaspects of the present disclosure are applied to Embodiment 1, forexample, any of the following may be performed.

(1) regarding the encoder or the decoder according to Embodiment 1,among components included in the encoder or the decoder according toEmbodiment 1, substituting a component corresponding to a componentpresented in the description of aspects of the present disclosure with acomponent presented in the description of aspects of the presentdisclosure;

(2) regarding the encoder or the decoder according to Embodiment 1,implementing discretionary changes to functions or implemented processesperformed by one or more components included in the encoder or thedecoder according to Embodiment 1, such as addition, substitution, orremoval, etc., of such functions or implemented processes, thensubstituting a component corresponding to a component presented in thedescription of aspects of the present disclosure with a componentpresented in the description of aspects of the present disclosure;

(3) regarding the method implemented by the encoder or the decoderaccording to Embodiment 1, implementing discretionary changes such asaddition of processes and/or substitution, removal of one or more of theprocesses included in the method, and then substituting a processescorresponding to a process presented in the description of aspects ofthe present disclosure with a process presented in the description ofaspects of the present disclosure;

(4) combining one or more components included in the encoder or thedecoder according to Embodiment 1 with a component presented in thedescription of aspects of the present disclosure, a component includingone or more functions included in a component presented in thedescription of aspects of the present disclosure, or a component thatimplements one or more processes implemented by a component presented inthe description of aspects of the present disclosure;

(5) combining a component including one or more functions included inone or more components included in the encoder or the decoder accordingto Embodiment 1, or a component that implements one or more processesimplemented by one or more components included in the encoder or thedecoder according to Embodiment 1 with a component presented in thedescription of aspects of the present disclosure, a component includingone or more functions included in a component presented in thedescription of aspects of the present disclosure, or a component thatimplements one or more processes implemented by a component presented inthe description of aspects of the present disclosure;

(6) regarding the method implemented by the encoder or the decoderaccording to Embodiment 1, among processes included in the method,substituting a process corresponding to a process presented in thedescription of aspects of the present disclosure with a processpresented in the description of aspects of the present disclosure; and

(7) combining one or more processes included in the method implementedby the encoder or the decoder according to Embodiment 1 with a processpresented in the description of aspects of the present disclosure.

Note that the implementation of the processes and/or configurationspresented in the description of aspects of the present disclosure is notlimited to the above examples. For example, the processes and/orconfigurations presented in the description of aspects of the presentdisclosure may be implemented in a device used for a purpose differentfrom the moving picture/picture encoder or the moving picture/picturedecoder disclosed in Embodiment 1. Moreover, the processes and/orconfigurations presented in the description of aspects of the presentdisclosure may be independently implemented. Moreover, processes and/orconfigurations described in different aspects may be combined.

[Encoder Outline]

First, the encoder according to Embodiment 1 will be outlined. FIG. 1 isa block diagram illustrating a functional configuration of encoder 100according to Embodiment 1. Encoder 100 is a moving picture/pictureencoder that encodes a moving picture/picture block by block.

As illustrated in FIG. 1 , encoder 100 is a device that encodes apicture block by block, and includes splitter 102, subtractor 104,transformer 106, quantizer 108, entropy encoder 110, inverse quantizer112, inverse transformer 114, adder 116, block memory 118, loop filter120, frame memory 122, intra predictor 124, inter predictor 126, andprediction controller 128.

Encoder 100 is realized as, for example, a generic processor and memory.In this case, when a software program stored in the memory is executedby the processor, the processor functions as splitter 102, subtractor104, transformer 106, quantizer 108, entropy encoder 110, inversequantizer 112, inverse transformer 114, adder 116, loop filter 120,intra predictor 124, inter predictor 126, and prediction controller 128.Alternatively, encoder 100 may be realized as one or more dedicatedelectronic circuits corresponding to splitter 102, subtractor 104,transformer 106, quantizer 108, entropy encoder 110, inverse quantizer112, inverse transformer 114, adder 116, loop filter 120, intrapredictor 124, inter predictor 126, and prediction controller 128.

Hereinafter, each component included in encoder 100 will be described.

[Splitter]

Splitter 102 splits each picture included in an input moving pictureinto blocks, and outputs each block to subtractor 104. For example,splitter 102 first splits a picture into blocks of a fixed size (forexample, 128×128). The fixed size block is also referred to as codingtree unit (CTU). Splitter 102 then splits each fixed size block intoblocks of variable sizes (for example, 64×64 or smaller), based onrecursive quad tree and/or binary tree block splitting. The variablesize block is also referred to as a coding unit (CU), a prediction unit(PU), or a transform unit (TU). Note that in this embodiment, there isno need to differentiate between CU, PU, and TU; all or some of theblocks in a picture may be processed per CU, PU, or TU.

FIG. 2 illustrates one example of block splitting according toEmbodiment 1. In FIG. 2 , the solid lines represent block boundaries ofblocks split by quad tree block splitting, and the dashed linesrepresent block boundaries of blocks split by binary tree blocksplitting.

Here, block 10 is a square 128×128 pixel block (128×128 block). This128×128 block 10 is first split into four square 64×64 blocks (quad treeblock splitting).

The top left 64×64 block is further vertically split into two rectangle32×64 blocks, and the left 32×64 block is further vertically split intotwo rectangle 16×64 blocks (binary tree block splitting). As a result,the top left 64×64 block is split into two 16×64 blocks 11 and 12 andone 32×64 block 13. The top right 64×64 block is horizontally split intotwo rectangle 64×32 blocks 14 and 15 (binary tree block splitting).

The bottom left 64×64 block is first split into four square 32×32 blocks(quad tree block splitting). The top left block and the bottom rightblock among the four 32×32 blocks are further split. The top left 32×32block is vertically split into two rectangle 16×32 blocks, and the right16×32 block is further horizontally split into two 16×16 blocks (binarytree block splitting). The bottom right 32×32 block is horizontallysplit into two 32×16 blocks (binary tree block splitting). As a result,the bottom left 64×64 block is split into 16×32 block 16, two 16×16blocks 17 and 18, two 32×32 blocks 19 and 20, and two 32×16 blocks 21and 22.

The bottom right 64×64 block 23 is not split.

As described above, in FIG. 2 , block 10 is split into 13 variable sizeblocks 11 through 23 based on recursive quad tree and binary tree blocksplitting. This type of splitting is also referred to as quad tree plusbinary tree (QTBT) splitting.

Note that in FIG. 2 , one block is split into four or two blocks (quadtree or binary tree block splitting), but splitting is not limited tothis example. For example, one block may be split into three blocks(ternary block splitting). Splitting including such ternary blocksplitting is also referred to as multi-type tree (MBT) splitting

[Subtractor]

Subtractor 104 subtracts a prediction signal (prediction sample) from anoriginal signal (original sample) per block split by splitter 102. Inother words, subtractor 104 calculates prediction errors (also referredto as residuals) of a block to be encoded (hereinafter referred to as acurrent block). Subtractor 104 then outputs the calculated predictionerrors to transformer 106.

The original signal is a signal input into encoder 100, and is a signalrepresenting an image for each picture included in a moving picture (forexample, a luma signal and two chroma signals). Hereinafter, a signalrepresenting an image is also referred to as a sample.

[Transformer]

Transformer 106 transforms spatial domain prediction errors intofrequency domain transform coefficients, and outputs the transformcoefficients to quantizer 108. More specifically, transformer 106applies, for example, a predefined discrete cosine transform (DCT) ordiscrete sine transform (DST) to spatial domain prediction errors.

Note that transformer 106 may adaptively select a transform type fromamong a plurality of transform types, and transform prediction errorsinto transform coefficients by using a transform basis functioncorresponding to the selected transform type. This sort of transform isalso referred to as explicit multiple core transform (EMT) or adaptivemultiple transform (AMT).

The transform types include, for example, DCT-II, DCT-V, DCT-VIII,DST-I, and DST-VII. FIG. 3 is a chart indicating transform basisfunctions for each transform type. In FIG. 3 , N indicates the number ofinput pixels. For example, selection of a transform type from among theplurality of transform types may depend on the prediction type (intraprediction and inter prediction), and may depend on intra predictionmode.

Information indicating whether to apply such EMT or AMT (referred to as,for example, an AMT flag) and information indicating the selectedtransform type is signalled at the CU level. Note that the signaling ofsuch information need not be performed at the CU level, and may beperformed at another level (for example, at the sequence level, picturelevel, slice level, tile level, or CTU level).

Moreover, transformer 106 may apply a secondary transform to thetransform coefficients (transform result). Such a secondary transform isalso referred to as adaptive secondary transform (AST) or non-separablesecondary transform (NSST). For example, transformer 106 applies asecondary transform to each sub-block (for example, each 4×4 sub-block)included in the block of the transform coefficients corresponding to theintra prediction errors. Information indicating whether to apply NSSTand information related to the transform matrix used in NSST aresignalled at the CU level. Note that the signaling of such informationneed not be performed at the CU level, and may be performed at anotherlevel (for example, at the sequence level, picture level, slice level,tile level, or CTU level).

Here, a separable transform is a method in which a transform isperformed a plurality of times by separately performing a transform foreach direction according to the number of dimensions input. Anon-separable transform is a method of performing a collective transformin which two or more dimensions in a multidimensional input arecollectively regarded as a single dimension.

In one example of a non-separable transform, when the input is a 4×4block, the 4×4 block is regarded as a single array including 16components, and the transform applies a 16×16 transform matrix to thearray.

Moreover, similar to above, after an input 4×4 block is regarded as asingle array including 16 components, a transform that performs aplurality of Givens rotations on the array (i.e., a Hypercube-GivensTransform) is also one example of a non-separable transform.

[Quantizer]

Quantizer 108 quantizes the transform coefficients output fromtransformer 106. More specifically, quantizer 108 scans, in apredetermined scanning order, the transform coefficients of the currentblock, and quantizes the scanned transform coefficients based onquantization parameters (QP) corresponding to the transformcoefficients. Quantizer 108 then outputs the quantized transformcoefficients (hereinafter referred to as quantized coefficients) of thecurrent block to entropy encoder 110 and inverse quantizer 112.

A predetermined order is an order for quantizing/inverse quantizingtransform coefficients. For example, a predetermined scanning order isdefined as ascending order of frequency (from low to high frequency) ordescending order of frequency (from high to low frequency).

A quantization parameter is a parameter defining a quantization stepsize (quantization width). For example, if the value of the quantizationparameter increases, the quantization step size also increases. In otherwords, if the value of the quantization parameter increases, thequantization error increases.

[Entropy Encoder]

Entropy encoder 110 generates an encoded signal (encoded bitstream) byvariable length encoding quantized coefficients, which are inputs fromquantizer 108. More specifically, entropy encoder 110, for example,binarizes quantized coefficients and arithmetic encodes the binarysignal.

[Inverse Quantizer]

Inverse quantizer 112 inverse quantizes quantized coefficients, whichare inputs from quantizer 108. More specifically, inverse quantizer 112inverse quantizes, in a predetermined scanning order, quantizedcoefficients of the current block. Inverse quantizer 112 then outputsthe inverse quantized transform coefficients of the current block toinverse transformer 114.

[Inverse Transformer]

Inverse transformer 114 restores prediction errors by inversetransforming transform coefficients, which are inputs from inversequantizer 112. More specifically, inverse transformer 114 restores theprediction errors of the current block by applying an inverse transformcorresponding to the transform applied by transformer 106 on thetransform coefficients. Inverse transformer 114 then outputs therestored prediction errors to adder 116.

Note that since information is lost in quantization, the restoredprediction errors do not match the prediction errors calculated bysubtractor 104. In other words, the restored prediction errors includequantization errors.

[Adder]

Adder 116 reconstructs the current block by summing prediction errors,which are inputs from inverse transformer 114, and prediction samples,which are inputs from prediction controller 128. Adder 116 then outputsthe reconstructed block to block memory 118 and loop filter 120. Areconstructed block is also referred to as a local decoded block.

[Block Memory]

Block memory 118 is storage for storing blocks in a picture to beencoded (hereinafter referred to as a current picture) for reference inintra prediction. More specifically, block memory 118 storesreconstructed blocks output from adder 116.

[Loop Filter]

Loop filter 120 applies a loop filter to blocks reconstructed by adder116, and outputs the filtered reconstructed blocks to frame memory 122.A loop filter is a filter used in an encoding loop (in-loop filter), andincludes, for example, a deblocking filter (DF), a sample adaptiveoffset (SAO), and an adaptive loop filter (ALF).

In ALF, a least square error filter for removing compression artifactsis applied. For example, one filter from among a plurality of filters isselected for each 2×2 sub-block in the current block based on directionand activity of local gradients, and is applied.

More specifically, first, each sub-block (for example, each 2×2sub-block) is categorized into one out of a plurality of classes (forexample, 15 or 25 classes). The classification of the sub-block is basedon gradient directionality and activity. For example, classificationindex C is derived based on gradient directionality D (for example, 0 to2 or 0 to 4) and gradient activity A (for example, 0 to 4) (for example,C=5D+A). Then, based on classification index C, each sub-block iscategorized into one out of a plurality of classes (for example, 15 or25 classes).

For example, gradient directionality D is calculated by comparinggradients of a plurality of directions (for example, the horizontal,vertical, and two diagonal directions). Moreover, for example, gradientactivity A is calculated by summing gradients of a plurality ofdirections and quantizing the sum.

The filter to be used for each sub-block is determined from among theplurality of filters based on the result of such categorization.

The filter shape to be used in ALF is, for example, a circular symmetricfilter shape. FIG. 4A through FIG. 4C illustrate examples of filtershapes used in ALF. FIG. 4A illustrates a 5×5 diamond shape filter, FIG.4B illustrates a 7×7 diamond shape filter, and FIG. 4C illustrates a 9×9diamond shape filter. Information indicating the filter shape issignalled at the picture level. Note that the signaling of informationindicating the filter shape need not be performed at the picture level,and may be performed at another level (for example, at the sequencelevel, slice level, tile level, CTU level, or CU level).

The enabling or disabling of ALF is determined at the picture level orCU level. For example, for luma, the decision to apply ALF or not isdone at the CU level, and for chroma, the decision to apply ALF or notis done at the picture level. Information indicating whether ALF isenabled or disabled is signalled at the picture level or CU level. Notethat the signaling of information indicating whether ALF is enabled ordisabled need not be performed at the picture level or CU level, and maybe performed at another level (for example, at the sequence level, slicelevel, tile level, or CTU level).

The coefficients set for the plurality of selectable filters (forexample, 15 or 25 filters) is signalled at the picture level. Note thatthe signaling of the coefficients set need not be performed at thepicture level, and may be performed at another level (for example, atthe sequence level, slice level, tile level, CTU level, CU level, orsub-block level).

[Frame Memory]

Frame memory 122 is storage for storing reference pictures used in interprediction, and is also referred to as a frame buffer. Morespecifically, frame memory 122 stores reconstructed blocks filtered byloop filter 120.

[Intra Predictor]

Intra predictor 124 generates a prediction signal (intra predictionsignal) by intra predicting the current block with reference to a blockor blocks in the current picture and stored in block memory 118 (alsoreferred to as intra frame prediction). More specifically, intrapredictor 124 generates an intra prediction signal by intra predictionwith reference to samples (for example, luma and/or chroma values) of ablock or blocks neighboring the current block, and then outputs theintra prediction signal to prediction controller 128.

For example, intra predictor 124 performs intra prediction by using onemode from among a plurality of predefined intra prediction modes. Theintra prediction modes include one or more non-directional predictionmodes and a plurality of directional prediction modes.

The one or more non-directional prediction modes include, for example,planar prediction mode and DC prediction mode defined in theH.265/high-efficiency video coding (HEVC) standard (see H.265 (ISO/IEC23008-2 HEVC (High Efficiency Video Coding))).

The plurality of directional prediction modes include, for example, the33 directional prediction modes defined in the H.265/HEVC standard. Notethat the plurality of directional prediction modes may further include32 directional prediction modes in addition to the 33 directionalprediction modes (for a total of 65 directional prediction modes). FIG.5A illustrates 67 intra prediction modes used in intra prediction (twonon-directional prediction modes and 65 directional prediction modes).The solid arrows represent the 33 directions defined in the H.265/HEVCstandard, and the dashed arrows represent the additional 32 directions.

Note that a luma block may be referenced in chroma block intraprediction. In other words, a chroma component of the current block maybe predicted based on a luma component of the current block. Such intraprediction is also referred to as cross-component linear model (CCLM)prediction. Such a chroma block intra prediction mode that references aluma block (referred to as, for example, CCLM mode) may be added as oneof the chroma block intra prediction modes.

Intra predictor 124 may correct post-intra-prediction pixel values basedon horizontal/vertical reference pixel gradients. Intra predictionaccompanied by this sort of correcting is also referred to as positiondependent intra prediction combination (PDPC). Information indicatingwhether to apply PDPC or not (referred to as, for example, a PDPC flag)is, for example, signalled at the CU level. Note that the signaling ofthis information need not be performed at the CU level, and may beperformed at another level (for example, on the sequence level, picturelevel, slice level, tile level, or CTU level).

[Inter Predictor]

Inter predictor 126 generates a prediction signal (inter predictionsignal) by inter predicting the current block with reference to a blockor blocks in a reference picture, which is different from the currentpicture and is stored in frame memory 122 (also referred to as interframe prediction). Inter prediction is performed per current block orper sub-block (for example, per 4×4 block) in the current block. Forexample, inter predictor 126 performs motion estimation in a referencepicture for the current block or sub-block. Inter predictor 126 thengenerates an inter prediction signal of the current block or sub-blockby motion compensation by using motion information (for example, amotion vector) obtained from motion estimation. Inter predictor 126 thenoutputs the generated inter prediction signal to prediction controller128.

The motion information used in motion compensation is signalled. Amotion vector predictor may be used for the signaling of the motionvector. In other words, the difference between the motion vector and themotion vector predictor may be signalled.

Note that the inter prediction signal may be generated using motioninformation for a neighboring block in addition to motion informationfor the current block obtained from motion estimation. Morespecifically, the inter prediction signal may be generated per sub-blockin the current block by calculating a weighted sum of a predictionsignal based on motion information obtained from motion estimation and aprediction signal based on motion information for a neighboring block.Such inter prediction (motion compensation) is also referred to asoverlapped block motion compensation (OBMC).

In such an OBMC mode, information indicating sub-block size for OBMC(referred to as, for example, OBMC block size) is signalled at thesequence level. Moreover, information indicating whether to apply theOBMC mode or not (referred to as, for example, an OBMC flag) issignalled at the CU level. Note that the signaling of such informationneed not be performed at the sequence level and CU level, and may beperformed at another level (for example, at the picture level, slicelevel, tile level, CTU level, or sub-block level).

Hereinafter, the OBMC mode will be described in further detail. FIG. 5Bis a flowchart and FIG. 5C is a conceptual diagram for illustrating anoutline of a prediction image correction process performed via OBMCprocessing.

First, a prediction image (Pred) is obtained through typical motioncompensation using a motion vector (MV) assigned to the current block.

Next, a prediction image (Pred_L) is obtained by applying a motionvector (MV_L) of the encoded neighboring left block to the currentblock, and a first pass of the correction of the prediction image ismade by superimposing the prediction image and Pred_L.

Similarly, a prediction image (Pred_U) is obtained by applying a motionvector (MV_U) of the encoded neighboring upper block to the currentblock, and a second pass of the correction of the prediction image ismade by superimposing the prediction image resulting from the first passand Pred_U. The result of the second pass is the final prediction image.

Note that the above example is of a two-pass correction method using theneighboring left and upper blocks, but the method may be a three-pass orhigher correction method that also uses the neighboring right and/orlower block.

Note that the region subject to superimposition may be the entire pixelregion of the block, and, alternatively, may be a partial block boundaryregion.

Note that here, the prediction image correction process is described asbeing based on a single reference picture, but the same applies when aprediction image is corrected based on a plurality of referencepictures. In such a case, after corrected prediction images resultingfrom performing correction based on each of the reference pictures areobtained, the obtained corrected prediction images are furthersuperimposed to obtain the final prediction image.

Note that the unit of the current block may be a prediction block and,alternatively, may be a sub-block obtained by further dividing theprediction block.

One example of a method for determining whether to implement OBMCprocessing is by using an obmc_flag, which is a signal that indicateswhether to implement OBMC processing. As one specific example, theencoder determines whether the current block belongs to a regionincluding complicated motion. The encoder sets the obmc_flag to a valueof “1” when the block belongs to a region including complicated motionand implements OBMC processing when encoding, and sets the obmc_flag toa value of “0” when the block does not belong to a region includingcomplication motion and encodes without implementing OBMC processing.The decoder switches between implementing OBMC processing or not bydecoding the obmc_flag written in the stream and performing the decodingin accordance with the flag value.

Note that the motion information may be derived on the decoder sidewithout being signalled. For example, a merge mode defined in theH.265/HEVC standard may be used. Moreover, for example, the motioninformation may be derived by performing motion estimation on thedecoder side. In this case, motion estimation is performed without usingthe pixel values of the current block.

Here, a mode for performing motion estimation on the decoder side willbe described. A mode for performing motion estimation on the decoderside is also referred to as pattern matched motion vector derivation(PMMVD) mode or frame rate up-conversion (FRUC) mode.

One example of FRUC processing is illustrated in FIG. 5D. First, acandidate list (a candidate list may be a merge list) of candidates eachincluding a motion vector predictor is generated with reference tomotion vectors of encoded blocks that spatially or temporally neighborthe current block. Next, the best candidate MV is selected from among aplurality of candidate MVs registered in the candidate list. Forexample, evaluation values for the candidates included in the candidatelist are calculated and one candidate is selected based on thecalculated evaluation values.

Next, a motion vector for the current block is derived from the motionvector of the selected candidate. More specifically, for example, themotion vector for the current block is calculated as the motion vectorof the selected candidate (best candidate MV), as-is. Alternatively, themotion vector for the current block may be derived by pattern matchingperformed in the vicinity of a position in a reference picturecorresponding to the motion vector of the selected candidate. In otherwords, when the vicinity of the best candidate MV is searched via thesame method and an MV having a better evaluation value is found, thebest candidate MV may be updated to the MV having the better evaluationvalue, and the MV having the better evaluation value may be used as thefinal MV for the current block. Note that a configuration in which thisprocessing is not implemented is also acceptable.

The same processes may be performed in cases in which the processing isperformed in units of sub-blocks.

Note that an evaluation value is calculated by calculating thedifference in the reconstructed image by pattern matching performedbetween a region in a reference picture corresponding to a motion vectorand a predetermined region. Note that the evaluation value may becalculated by using some other information in addition to thedifference.

The pattern matching used is either first pattern matching or secondpattern matching. First pattern matching and second pattern matching arealso referred to as bilateral matching and template matching,respectively.

In the first pattern matching, pattern matching is performed between twoblocks along the motion trajectory of the current block in two differentreference pictures. Therefore, in the first pattern matching, a regionin another reference picture conforming to the motion trajectory of thecurrent block is used as the predetermined region for theabove-described calculation of the candidate evaluation value.

FIG. 6 is for illustrating one example of pattern matching (bilateralmatching) between two blocks along a motion trajectory. As illustratedin FIG. 6 , in the first pattern matching, two motion vectors (MV0, MV1)are derived by finding the best match between two blocks along themotion trajectory of the current block (Cur block) in two differentreference pictures (Ref0, Ref1). More specifically, a difference between(i) a reconstructed image in a specified position in a first encodedreference picture (Ref0) specified by a candidate MV and (ii) areconstructed picture in a specified position in a second encodedreference picture (Ref1) specified by a symmetrical MV scaled at adisplay time interval of the candidate MV may be derived, and theevaluation value for the current block may be calculated by using thederived difference. The candidate MV having the best evaluation valueamong the plurality of candidate MVs may be selected as the final MV.

Under the assumption of continuous motion trajectory, the motion vectors(MV0, MV1) pointing to the two reference blocks shall be proportional tothe temporal distances (TD0, TD1) between the current picture (Cur Pic)and the two reference pictures (Ref0, Ref1). For example, when thecurrent picture is temporally between the two reference pictures and thetemporal distance from the current picture to the two reference picturesis the same, the first pattern matching derives a mirror basedbi-directional motion vector.

In the second pattern matching, pattern matching is performed between atemplate in the current picture (blocks neighboring the current block inthe current picture (for example, the top and/or left neighboringblocks)) and a block in a reference picture. Therefore, in the secondpattern matching, a block neighboring the current block in the currentpicture is used as the predetermined region for the above-describedcalculation of the candidate evaluation value.

FIG. 7 is for illustrating one example of pattern matching (templatematching) between a template in the current picture and a block in areference picture. As illustrated in FIG. 7 , in the second patternmatching, a motion vector of the current block is derived by searching areference picture (Ref0) to find the block that best matches neighboringblocks of the current block (Cur block) in the current picture (CurPic). More specifically, a difference between (i) a reconstructed imageof an encoded region that is both or one of the neighboring left andneighboring upper region and (ii) a reconstructed picture in the sameposition in an encoded reference picture (Ref0) specified by a candidateMV may be derived, and the evaluation value for the current block may becalculated by using the derived difference. The candidate MV having thebest evaluation value among the plurality of candidate MVs may beselected as the best candidate MV.

Information indicating whether to apply the FRUC mode or not (referredto as, for example, a FRUC flag) is signalled at the CU level. Moreover,when the FRUC mode is applied (for example, when the FRUC flag is set totrue), information indicating the pattern matching method (first patternmatching or second pattern matching) is signalled at the CU level. Notethat the signaling of such information need not be performed at the CUlevel, and may be performed at another level (for example, at thesequence level, picture level, slice level, tile level, CTU level, orsub-block level).

Here, a mode for deriving a motion vector based on a model assuminguniform linear motion will be described. This mode is also referred toas a bi-directional optical flow (BIO) mode.

FIG. 8 is for illustrating a model assuming uniform linear motion. InFIG. 8 , (v_(x), v_(y)) denotes a velocity vector, and τ₀ and τ₁ denotetemporal distances between the current picture (Cur Pic) and tworeference pictures (Ref₀, Ref₁). (MVx₀, MVy₀) denotes a motion vectorcorresponding to reference picture Ref₀, and (MVx₁, MVy₁) denotes amotion vector corresponding to reference picture Ref₁.

Here, under the assumption of uniform linear motion exhibited byvelocity vector (v_(x), v_(y)), (MVx₀, MVy₀) and (MVx₁, MVy₁) arerepresented as (v_(x)τ₀, v_(y)τ₀) and (−v_(x)τ₁, −v_(y)τ₁),respectively, and the following optical flow equation is given.

[Math. 1]

∂I ^((k)) /∂t+v _(x) ∂I ^((k)) /∂x+v _(y) ∂I ^((k)) /∂y=0.  (1)

Here, I^((k)) denotes a luma value from reference picture k (k=0, 1)after motion compensation. This optical flow equation shows that the sumof (i) the time derivative of the luma value, (ii) the product of thehorizontal velocity and the horizontal component of the spatial gradientof a reference picture, and (iii) the product of the vertical velocityand the vertical component of the spatial gradient of a referencepicture is equal to zero. A motion vector of each block obtained from,for example, a merge list is corrected pixel by pixel based on acombination of the optical flow equation and Hermite interpolation.

Note that a motion vector may be derived on the decoder side using amethod other than deriving a motion vector based on a model assuminguniform linear motion. For example, a motion vector may be derived foreach sub-block based on motion vectors of neighboring blocks.

Here, a mode in which a motion vector is derived for each sub-blockbased on motion vectors of neighboring blocks will be described. Thismode is also referred to as affine motion compensation prediction mode.

FIG. 9A is for illustrating deriving a motion vector of each sub-blockbased on motion vectors of neighboring blocks. In FIG. 9A, the currentblock includes 16 4×4 sub-blocks. Here, motion vector v₀ of the top leftcorner control point in the current block is derived based on motionvectors of neighboring sub-blocks, and motion vector v₁ of the top rightcorner control point in the current block is derived based on motionvectors of neighboring blocks. Then, using the two motion vectors v₀ andv₁, the motion vector (v_(x), v_(y)) of each sub-block in the currentblock is derived using Equation 2 below.

$\begin{matrix}\left\lbrack {{Math}.2} \right\rbrack &  \\\left\{ \begin{matrix}{v_{x} = {{\frac{\left( {v_{1x} - v_{0x}} \right)}{w}x} - {\frac{\left( {v_{1y} - v_{0y}} \right)}{w}y} + v_{0x}}} \\{v_{y} = {{\frac{\left( {v_{1y} - v_{0y}} \right)}{w}x} + {\frac{\left( {v_{1x} - v_{0x}} \right)}{w}y} + v_{0y}}}\end{matrix} \right. & (2)\end{matrix}$

Here, x and y are the horizontal and vertical positions of thesub-block, respectively, and w is a predetermined weighted coefficient.

Such an affine motion compensation prediction mode may include a numberof modes of different methods of deriving the motion vectors of the topleft and top right corner control points. Information indicating such anaffine motion compensation prediction mode (referred to as, for example,an affine flag) is signalled at the CU level. Note that the signaling ofinformation indicating the affine motion compensation prediction modeneed not be performed at the CU level, and may be performed at anotherlevel (for example, at the sequence level, picture level, slice level,tile level, CTU level, or sub-block level).

[Prediction Controller]

Prediction controller 128 selects either the intra prediction signal orthe inter prediction signal, and outputs the selected prediction signalto subtractor 104 and adder 116.

Here, an example of deriving a motion vector via merge mode in a currentpicture will be given. FIG. 9B is for illustrating an outline of aprocess for deriving a motion vector via merge mode.

First, an MV predictor list in which candidate MV predictors areregistered is generated. Examples of candidate MV predictors include:spatially neighboring MV predictors, which are MVs of encoded blockspositioned in the spatial vicinity of the current block; a temporallyneighboring MV predictor, which is an MV of a block in an encodedreference picture that neighbors a block in the same location as thecurrent block; a combined MV predictor, which is an MV generated bycombining the MV values of the spatially neighboring MV predictor andthe temporally neighboring MV predictor; and a zero MV predictor, whichis an MV whose value is zero.

Next, the MV of the current block is determined by selecting one MVpredictor from among the plurality of MV predictors registered in the MVpredictor list.

Furthermore, in the variable-length encoder, a merge_idx, which is asignal indicating which MV predictor is selected, is written and encodedinto the stream.

Note that the MV predictors registered in the MV predictor listillustrated in FIG. 9B constitute one example. The number of MVpredictors registered in the MV predictor list may be different from thenumber illustrated in FIG. 9B, the MV predictors registered in the MVpredictor list may omit one or more of the types of MV predictors givenin the example in FIG. 9B, and the MV predictors registered in the MVpredictor list may include one or more types of MV predictors inaddition to and different from the types given in the example in FIG.9B.

Note that the final MV may be determined by performing DMVR processing(to be described later) by using the MV of the current block derived viamerge mode.

Here, an example of determining an MV by using DMVR processing will begiven.

FIG. 9C is a conceptual diagram for illustrating an outline of DMVRprocessing.

First, the most appropriate MVP set for the current block is consideredto be the candidate MV, reference pixels are obtained from a firstreference picture, which is a picture processed in the LO direction inaccordance with the candidate MV, and a second reference picture, whichis a picture processed in the Li direction in accordance with thecandidate MV, and a template is generated by calculating the average ofthe reference pixels.

Next, using the template, the surrounding regions of the candidate MVsof the first and second reference pictures are searched, and the MV withthe lowest cost is determined to be the final MV. Note that the costvalue is calculated using, for example, the difference between eachpixel value in the template and each pixel value in the regionssearched, as well as the MV value.

Note that the outlines of the processes described here are fundamentallythe same in both the encoder and the decoder.

Note that processing other than the processing exactly as describedabove may be used, so long as the processing is capable of deriving thefinal MV by searching the surroundings of the candidate MV.

Here, an example of a mode that generates a prediction image by usingLIC processing will be given.

FIG. 9D is for illustrating an outline of a prediction image generationmethod using a luminance correction process performed via LICprocessing.

First, an MV is extracted for obtaining, from an encoded referencepicture, a reference image corresponding to the current block.

Next, information indicating how the luminance value changed between thereference picture and the current picture is extracted and a luminancecorrection parameter is calculated by using the luminance pixel valuesfor the encoded left neighboring reference region and the encoded upperneighboring reference region, and the luminance pixel value in the samelocation in the reference picture specified by the MV.

The prediction image for the current block is generated by performing aluminance correction process by using the luminance correction parameteron the reference image in the reference picture specified by the MV.

Note that the shape of the surrounding reference region illustrated inFIG. 9D is just one example; the surrounding reference region may have adifferent shape.

Moreover, although a prediction image is generated from a singlereference picture in this example, in cases in which a prediction imageis generated from a plurality of reference pictures as well, theprediction image is generated after performing a luminance correctionprocess, via the same method, on the reference images obtained from thereference pictures.

One example of a method for determining whether to implement LICprocessing is by using an lic_flag, which is a signal that indicateswhether to implement LIC processing. As one specific example, theencoder determines whether the current block belongs to a region ofluminance change. The encoder sets the lic_flag to a value of “1” whenthe block belongs to a region of luminance change and implements LICprocessing when encoding, and sets the lic_flag to a value of “0” whenthe block does not belong to a region of luminance change and encodeswithout implementing LIC processing. The decoder switches betweenimplementing LIC processing or not by decoding the lic_flag written inthe stream and performing the decoding in accordance with the flagvalue.

One example of a different method of determining whether to implementLIC processing is determining so in accordance with whether LICprocessing was determined to be implemented for a surrounding block. Inone specific example, when merge mode is used on the current block,whether LIC processing was applied in the encoding of the surroundingencoded block selected upon deriving the MV in the merge mode processingmay be determined, and whether to implement LIC processing or not can beswitched based on the result of the determination. Note that in thisexample, the same applies to the processing performed on the decoderside.

[Decoder Outline]

Next, a decoder capable of decoding an encoded signal (encodedbitstream) output from encoder 100 will be described. FIG. 10 is a blockdiagram illustrating a functional configuration of decoder 200 accordingto Embodiment 1. Decoder 200 is a moving picture/picture decoder thatdecodes a moving picture/picture block by block.

As illustrated in FIG. 10 , decoder 200 includes entropy decoder 202,inverse quantizer 204, inverse transformer 206, adder 208, block memory210, loop filter 212, frame memory 214, intra predictor 216, interpredictor 218, and prediction controller 220.

Decoder 200 is realized as, for example, a generic processor and memory.In this case, when a software program stored in the memory is executedby the processor, the processor functions as entropy decoder 202,inverse quantizer 204, inverse transformer 206, adder 208, loop filter212, intra predictor 216, inter predictor 218, and prediction controller220. Alternatively, decoder 200 may be realized as one or more dedicatedelectronic circuits corresponding to entropy decoder 202, inversequantizer 204, inverse transformer 206, adder 208, loop filter 212,intra predictor 216, inter predictor 218, and prediction controller 220.

Hereinafter, each component included in decoder 200 will be described.

[Entropy Decoder]

Entropy decoder 202 entropy decodes an encoded bitstream. Morespecifically, for example, entropy decoder 202 arithmetic decodes anencoded bitstream into a binary signal. Entropy decoder 202 thendebinarizes the binary signal. With this, entropy decoder 202 outputsquantized coefficients of each block to inverse quantizer 204.

[Inverse Quantizer]

Inverse quantizer 204 inverse quantizes quantized coefficients of ablock to be decoded (hereinafter referred to as a current block), whichare inputs from entropy decoder 202. More specifically, inversequantizer 204 inverse quantizes quantized coefficients of the currentblock based on quantization parameters corresponding to the quantizedcoefficients. Inverse quantizer 204 then outputs the inverse quantizedcoefficients (i.e., transform coefficients) of the current block toinverse transformer 206.

[Inverse Transformer]

Inverse transformer 206 restores prediction errors by inversetransforming transform coefficients, which are inputs from inversequantizer 204.

For example, when information parsed from an encoded bitstream indicatesapplication of EMT or AMT (for example, when the AMT flag is set totrue), inverse transformer 206 inverse transforms the transformcoefficients of the current block based on information indicating theparsed transform type.

Moreover, for example, when information parsed from an encoded bitstreamindicates application of NSST, inverse transformer 206 applies asecondary inverse transform to the transform coefficients.

[Adder]

Adder 208 reconstructs the current block by summing prediction errors,which are inputs from inverse transformer 206, and prediction samples,which is an input from prediction controller 220. Adder 208 then outputsthe reconstructed block to block memory 210 and loop filter 212.

[Block Memory]

Block memory 210 is storage for storing blocks in a picture to bedecoded (hereinafter referred to as a current picture) for reference inintra prediction. More specifically, block memory 210 storesreconstructed blocks output from adder 208.

[Loop Filter]

Loop filter 212 applies a loop filter to blocks reconstructed by adder208, and outputs the filtered reconstructed blocks to frame memory 214and, for example, a display device.

When information indicating the enabling or disabling of ALF parsed froman encoded bitstream indicates enabled, one filter from among aplurality of filters is selected based on direction and activity oflocal gradients, and the selected filter is applied to the reconstructedblock.

[Frame Memory]

Frame memory 214 is storage for storing reference pictures used in interprediction, and is also referred to as a frame buffer. Morespecifically, frame memory 214 stores reconstructed blocks filtered byloop filter 212.

[Intra Predictor]

Intra predictor 216 generates a prediction signal (intra predictionsignal) by intra prediction with reference to a block or blocks in thecurrent picture and stored in block memory 210. More specifically, intrapredictor 216 generates an intra prediction signal by intra predictionwith reference to samples (for example, luma and/or chroma values) of ablock or blocks neighboring the current block, and then outputs theintra prediction signal to prediction controller 220.

Note that when an intra prediction mode in which a chroma block is intrapredicted from a luma block is selected, intra predictor 216 may predictthe chroma component of the current block based on the luma component ofthe current block.

Moreover, when information indicating the application of PDPC is parsedfrom an encoded bitstream, intra predictor 216 correctspost-intra-prediction pixel values based on horizontal/verticalreference pixel gradients.

[Inter Predictor]

Inter predictor 218 predicts the current block with reference to areference picture stored in frame memory 214. Inter prediction isperformed per current block or per sub-block (for example, per 4×4block) in the current block. For example, inter predictor 218 generatesan inter prediction signal of the current block or sub-block by motioncompensation by using motion information (for example, a motion vector)parsed from an encoded bitstream, and outputs the inter predictionsignal to prediction controller 220.

Note that when the information parsed from the encoded bitstreamindicates application of OBMC mode, inter predictor 218 generates theinter prediction signal using motion information for a neighboring blockin addition to motion information for the current block obtained frommotion estimation.

Moreover, when the information parsed from the encoded bitstreamindicates application of FRUC mode, inter predictor 218 derives motioninformation by performing motion estimation in accordance with thepattern matching method (bilateral matching or template matching) parsedfrom the encoded bitstream. Inter predictor 218 then performs motioncompensation using the derived motion information.

Moreover, when BIO mode is to be applied, inter predictor 218 derives amotion vector based on a model assuming uniform linear motion. Moreover,when the information parsed from the encoded bitstream indicates thataffine motion compensation prediction mode is to be applied, interpredictor 218 derives a motion vector of each sub-block based on motionvectors of neighboring blocks.

[Prediction Controller]

Prediction controller 220 selects either the intra prediction signal orthe inter prediction signal, and outputs the selected prediction signalto adder 208.

Embodiment 2

The encoding process and decoding process according to Embodiment 2 willbe described in detail with reference to FIG. 11 and FIG. 12 , and theencoder and decoder according to Embodiment 2 will be described indetail with reference to FIG. 15 and FIG. 16 .

[Encoding Process]

FIG. 11 illustrates a video encoding process according to Embodiment 2.

First, in step S1001, a first parameter for identifying, from aplurality of partition modes, a partition mode for partitioning a firstblock into sub blocks is written into a bitstream. Using a partitionmode will result in partitioning a block into sub blocks. Usingdifferent partition modes can result in partitioning a block into subblocks with different shapes, or different heights, or different widths.

FIG. 28 illustrates examples of partition modes for partitioning a Npixels by N pixels block in Embodiment 2. In FIG. 28 , (a) to (h) showdifferent partition modes. As illustrated in FIG. 28 , using partitionmode (a) will partition a N pixels by N pixels block (value of ‘N’ canbe any value in the range from 8 to 128 which are integer multiples of4, for example a 16 pixels by 16 pixels block) into two N/2 pixels by Npixels sub blocks (for example, 8 pixels by 16 pixels sub blocks). Usingpartition mode (b) will partition a N pixels by N pixels block into aN/4 pixels by N pixels sub block and a 3N/4 pixels by N pixels sub block(for example, a 4 pixels by 16 pixels sub block and a 12 pixels by 16pixels sub block). Using partition mode (c) will partition a N pixels byN pixels block into a 3N/4 pixels by N pixels sub block and a N/4 pixelsby N pixels sub block (for example, a 12 pixels by 16 pixels sub blockand a 4 pixels by 16 pixels sub block). Using partition mode (d) willpartition a N pixels by N pixels block into a N/4 pixels by N pixels subblock, a N/2 pixels by N pixels sub block, and a N/4 pixels by N pixelssub block (for example, a 4 pixels by 16 pixels sub block, a 8 pixels by16 pixels sub block and a 4 pixels by 16 pixels sub block). Usingpartition mode (e) will partition a N pixels by N pixels block into twoN pixels by N/2 pixels sub blocks (for example, 16 pixels by 8 pixelssub blocks). Using partition mode (f) will partition a N pixels by Npixels block into a N pixels by N/4 pixels sub block and a N pixels by3N/4 pixels sub block (for example, a 16 pixels by 4 pixels sub blockand a 16 pixels by 12 pixels sub block). Using partition mode (g) willpartition a N pixels by N pixels block into a N pixels by 3N/4 pixelssub block and a N pixels by N/4 pixels sub block (for example, a 16pixels by 12 pixels sub block and a 16 pixels by 4 pixels sub block).Using partition mode (h) will partition a N pixels by N pixels blockinto a N pixels by N/4 pixels sub block, a N pixels by N/2 pixels subblock, and a N pixels by N/4 pixels sub block (for example, a 16 pixelsby 4 pixels sub block, a 16 pixels by 8 pixels sub block and a 16 pixelsby 4 pixels sub block).

Next, in step S1002, it is determined if a first parameter identifies afirst partition mode.

Next, in step S1003, based on at least the determination whether thefirst parameter identifies a first partition mode, it is determined if asecond partition mode is not to be selected as a candidate forpartitioning a second block.

Two different sets of partition modes may split a block into sub blocksof same shapes and sizes. For example, as illustrated in FIG. 31A, subblocks from (1 b) and (2 c) have same shapes and sizes. A set ofpartition modes can include at least two partition modes. For example, aset of partition modes can include a ternary tree vertical splitfollowed by a binary tree vertical split on the center sub block and nosplit on other sub blocks as illustrated in (1 a) and (1 b) in FIG. 31A.Another set of partition modes, for example, can include a binary treevertical split followed by a binary tree vertical split on both of thesub blocks as illustrated in (2 a), (2 b), and (2 c) in FIG. 31A. Bothsets of partition modes will result in sub blocks of same shapes andsizes.

When selecting among two sets of partition modes that result insplitting a block into sub blocks of same shapes and sizes and each setsof partition modes, when encoded in a bit stream, have different numberof bins or different number of bits, the set of partition modes that hasfewer number of bins or fewer number of bits is selected among the twosets. Note that the number of bins and the number of bits is equivalentto the amount of code.

When selecting among two sets of partition modes that result insplitting a block into sub blocks of same shapes and sizes and each ofthe sets of partition modes, when encoded in a bit stream, have the samenumber of bins or same number of bits, the set of partition modes thatappears first in a predetermined order of a plurality of sets ofpartition modes is selected among the two sets. An example of thepredetermined order may be an order based on the number of partitionmodes in each set of partition modes.

FIG. 31A and FIG. 31B illustrate an example of splitting a block intosub blocks using a set of partition modes with fewer bins in theencoding partition modes. In this example, when the left N pixels by Npixels block is vertically split into two sub blocks, the secondpartition mode in step (2c), for the right N pixels by N pixels block isnot selected. This is because, in the partition mode encoding method inFIG. 31B, the second set of partition modes (2 a, 2 b, 2 c) will requiremore bins for the encoding of the partition mode as compared to thefirst set of partition modes (1 a, 1 b).

FIG. 32A to FIG. 32C illustrate an example of splitting a block into subblocks using a set of partition modes that appears first in apredetermined order of a plurality of sets of partition modes. In thisexample, when the top 2N pixels by N/2 pixels block is vertically splitinto three sub blocks, the second partition mode in step (2c), for thebottom 2N pixels by N/2 pixels block is not selected. This is because,in the partition mode encoding method in FIG. 32B, the second set ofpartition modes (2 a, 2 b, 2 c) has the same number of bins as the firstset of partition modes (1 a, 1 b, 1 c, 1 d) and appears after the firstset of partition modes (1 a, 1 b, 1 c, 1 d) in the predetermined orderof sets of partitions modes in FIG. 32C. The predetermined order of theplurality sets of partition modes can be fixed or signalled in abitstream.

FIG. 20 illustrates an example in which a second partition mode is notselected for partitioning a 2N pixels by N pixels block, as illustratedin step (2c), in Embodiment 2. As illustrated in FIG. 20 , a 2N pixelsby 2N pixels block (for example, a 16 pixels by 16 pixels block) can besplit into four equal sub blocks of size N pixels by N pixels (forexample, 8 pixels by 8 pixels) using a first way of splitting (i), as instep (1a). Furthermore, a 2N pixels by 2N pixels block can also be splitinto two equal sub blocks of size 2N pixels by N pixels (for example, 16pixels by 8 pixels) using a second way of splitting (2 a), as in step(2a). During the second way of splitting (ii), when first partition modesplits the top 2N pixels by N pixels block (first block) vertically intotwo N pixels by N pixels sub blocks as in step (2b), the secondpartition mode which vertically splits the bottom 2N pixels by N pixelsblock (second block) into two N pixels by N pixels sub blocks in step(2c) is not selected as a candidate for possible partition mode. This isbecause the second partition mode will produce sub blocks sizes same asthe quad split sub block sizes from the first way of splitting (i).

In this manner, in FIG. 20 , when the first block is vertically splitinto two equal sub blocks if the first partition mode is used, and thesecond block vertically neighboring the first block is vertically splitinto two equal sub blocks if the second partition mode is used, thesecond partition mode is not selected as a candidate.

FIG. 21 illustrates an example in which a second partition mode is notselected for partitioning a N pixels by 2N pixels block, as illustratedin step (2c), in Embodiment 2. As illustrated in FIG. 21 , a 2N pixelsby 2N pixels block can be split into four equal sub blocks of N pixelsby N pixels using the first way of splitting (i). Furthermore, as instep (2a), a 2N pixels by 2N pixels block can also be vertically splitinto two equal sub blocks of N pixels by 2N pixels (for example, 8pixels by 16 pixels) using the second way of splitting (ii). During thesecond way of splitting (ii), when first partition mode splits the leftN pixels by 2N pixels block (first block) horizontally into two N pixelsby N pixels sub blocks as in step (2b), the second partition mode whichhorizontally splits the right N pixels by 2N pixels block (second block)into two N pixels by N pixels sub blocks in step (2c) is not selected asa candidate for possible partition mode. This is because the secondpartition mode will produce sub blocks sizes same as the quad split subblock sizes from the first way of splitting (i).

In this manner, in FIG. 21 , when the first block is horizontally splitinto two equal sub blocks if the first partition mode is used, and thesecond block horizontally neighboring the first block is horizontallysplit into two equal sub blocks if the second partition mode is used,the second partition mode is not selected as a candidate.

FIG. 40 illustrates an example in which a 4N×2N partition in FIG. 20 issplit in three in a 1:2:1 ratio such as N×2N, 2N×2N, and N×2N. Here,when the upper block is to be split in three, a partition mode forsplitting the lower block in three in a 1:2:1 ratio is not selected as acandidate for possible partition mode. The splitting into three may beperformed in a ratio different from 1:2:1. In addition, splitting intomore than 3 may be performed, and, even when splitting into two, theratio may be different from 1:1, such as 1:2 or 1:3. Although FIG. 40illustrates an example of splitting horizontally first, the samerestriction can also be applied when splitting vertically first.

FIG. 41 and FIG. 42 illustrate an example in which the same restrictionis applied in the case where the first block is a rectangle.

FIG. 43 illustrates an example of a second restriction when a square ishorizontally split in three and further horizontally split into twoequal parts. When applying the restriction in FIG. 43 , in FIG. 40 , itis possible to select a partition mode for splitting the 4N×2N lowerblock in three in a 1:2:3 ratio. Information indicating which of therestriction in FIG. 40 and the restriction in FIG. 43 is to be appliedmay be separately encoded in header information. Alternatively, therestriction having a smaller amount of code of information indicatingthe partition may be applied. For example, assuming that the amount ofcodes of information indicating the partition in case 1 and case 2 is asshown below, the splitting of case 1 is enabled and the splitting ofcase 2 is disabled. In other words, the restriction in FIG. 43 isapplied.

(Case 1) (1) After a square is horizontally split into two, (2) each ofthe two rectangular blocks at the top and bottom is vertically splitinto three: (1) direction information: 1 bit, number-of-partitionsinformation: 1 bit, (2) (direction information: 1 bit,number-of-partitions information: 1 bit)×2 for a total of 6 bits(Case 2) (1) After a square is vertically split, (2) each of left,center, and right rectangular blocks is horizontally split in two: (1)direction information: 1 bit, number-of-partitions information: 1 bit,(2) (direction information: 1 bit, number-of-partitions information: 1bit)×3 for a total of 8 bits

Alternatively, during encoding, there are instances where theappropriate partition is determined while selecting a partition mode ina predetermined order. For example, it is possible to try splitting intotwo, then try splitting into three or splitting into four (2 equal partshorizontally and vertically), etc. At this time, before the trial forsplitting into three as in FIG. 43 , a trial that starts from splittinginto two as in the examples in FIG. 40 has already been performed.Therefore, in a trial that starts from splitting into two, therestriction in FIG. 43 is applied because partitions resulting fromequally splitting a block horizontally, and further vertically splittingthe two blocks at the top and bottom into three is already obtained. Inthis manner, the restriction method to be selected may be determinedbased on a predetermined encoding scheme.

FIG. 44 illustrates an example where, in the second partitioning mode,the selectable partition modes for partitioning the second block in thesame direction as the first partition mode are restricted. Here, thefirst partition mode is vertically splitting into three, and thus, atthis time, splitting into two cannot be selected as the second partitionmode. On the other hand, splitting into two can be selected for thevertical direction which is a different direction from the firstpartition mode (FIG. 45 ).

FIG. 22 illustrates an example in which a second partition mode is notselected for partitioning a N pixels by N pixels block, as illustratedin step (2c), in Embodiment 2. As illustrated in FIG. 22 , a 2N pixelsby N pixels (value of ‘N’ can be any value in the range from 8 to 128which are integer multiples of 4, for example, 16 pixels by 8 pixels)block can be split vertically into a N/2 pixels by N pixels sub block, aN pixels by N pixels sub block, and a N/2 pixels by N pixels sub block(for example, a 4 pixels by 8 pixels sub block, a 8 pixels by 8 pixelssub block, a 4 pixels by 8 pixels sub block), using the first way ofsplitting (i), as in step (1a). Furthermore, a 2N pixels by N pixelsblock can also be split into two N pixels by N pixels sub blocks usingthe second way of splitting (ii), as in step (2a). During the first wayof splitting (i), the center N pixels by N pixels block can bevertically split into two N/2 pixels by N pixels (for example, 4 pixelsby 8 pixels) sub blocks in step (1b). During the second way of splitting(ii), when the left N pixels by N pixels block (first block) isvertically split into two N/2 pixels by N pixels sub blocks as in step(2b), a partition mode which vertically splits the right N pixels by Npixels block (second block) into two N/2 pixels by N pixels sub blocksin step (2c) is not selected as a candidate for possible partition mode.This is because, the partition mode will produce sub blocks sizes whichare the same as that obtained from the first way of splitting (i), orfour N/2 pixels by N pixels sub blocks.

In this manner, in FIG. 22 , when the first block is vertically splitinto two equal sub blocks if the first partition mode is used, and thesecond block horizontally neighboring the first block is verticallysplit into two equal sub blocks if the second partition mode is used,the second partition mode is not selected as a candidate.

FIG. 23 illustrates an example in which a second partition mode is notselected for partitioning a N pixels by N pixels block, as illustratedin step (2c), in Embodiment 2. As illustrated in FIG. 23 , a N pixels by2N pixels (value of ‘N’ can be any value in the range from 8 to 128which are integer multiples of 4, for example, 8 pixels by 16 pixels)block can be split into a N pixels by N/2 pixels sub block, a N pixelsby N pixels sub block, and a N pixels by N/2 pixels sub block (forexample, a 8 pixels by 4 pixels sub block, a 8 pixels by 8 pixels subblock, a 8 pixels by 4 pixels sub block) using the first way ofsplitting (i), as in step (1a). Furthermore, a N pixels by 2N pixelsblock can also be split into two N pixels by N pixels sub blocks usingthe second way of splitting, as in step (2a). During the first way ofsplitting (i), the center N pixels by N pixels block can be horizontallysplit into two N pixels by N/2 pixels sub blocks, as in step (1b).During the second way of splitting (ii), when the top N pixels by Npixels (first block) is horizontally split into two N pixels by N/2pixels sub blocks in step (2b), a partition mode which horizontallysplits the bottom N pixels by N pixels (second block) into two N pixelsby N/2 pixels sub blocks in step (2c) is not selected as a candidate forpossible partition mode. This is because, the partition mode willproduce sub blocks sizes which are the same as that obtained from thefirst way of splitting (i), or four N pixels by N/2 pixels sub blocks.

In this manner, in FIG. 23 , when the first block is horizontally splitinto two equal sub blocks if the first partition mode is used, and thesecond block vertically neighboring the first block is horizontallysplit into two equal sub blocks if the second partition mode is used,the second partition mode is not selected as a candidate.

If it is determined that the second partition mode is to be selected asa candidate for partitioning a second block (N in S1003), a partitionmode is selected from a plurality of partition modes which include thesecond partition mode as a candidate in step S1004. In step S1005, asecond parameter indicating the selection result is written into abitstream.

If it is determined that the second partition mode is not to be selectedas a candidate for partitioning a second block (Y in S1003), a partitionmode different from the second partition mode is selected forpartitioning the second block in step S1006. Here, the selectedpartition mode partitions a block into sub blocks with different shapesor different sizes as compared to sub blocks that would have beengenerated by the second partition mode.

FIG. 24 illustrates an example of partitioning a 2N pixels by N pixelsblock using a partition mode selected when the second partition mode isnot to be selected, as illustrated in step (3), in Embodiment 2. Asillustrated in FIG. 24 , the selected partition mode can split a current2N pixels by N pixels block (the bottom block in this example) intothree sub blocks as illustrated in (c) and (f) in FIG. 24 . The sizes ofthe three sub blocks may be different. For example, among the three subblocks, a large sub block may have two times the width/height of a smallsub block. Furthermore, for example, the selected partition mode cansplit the current block into two sub blocks with different sizes(asymmetrical binary tree) as illustrated in (a), (b), (d), and (e) inFIG. 24 . For example, when an asymmetrical binary tree is used, thelarge sub block can have three times the width/height of the small subblock.

FIG. 25 illustrates an example of partitioning a N pixels by 2N pixelsblock using a partition mode selected when the second partition mode isnot to be selected, as illustrated in step (3), in Embodiment 2. Asillustrated in FIG. 25 , the selected partition mode can split thecurrent N pixels by 2N pixels block (the right block in this example)into three sub blocks as illustrated in (c) and (f) in FIG. 25 . Thesizes of the three sub blocks may be different. For example, among thethree sub blocks, a large sub block may have two times the width/heightof a small sub block. Furthermore, for example, the selected partitionmode can split the current block into two sub blocks with differentsizes (asymmetrical binary tree) as illustrated in (a), (b), (d), and(e) in FIG. 25 . For example, when an asymmetrical binary tree is used,the large sub block can have three times the width/height of the smallsub block.

FIG. 26 illustrates an example of partitioning a N pixels by N pixelsblock using a partition mode selected when the second partition mode isnot to be selected, as illustrated in step (3), in Embodiment 2. Asillustrated in FIG. 26 , a 2N pixels by N pixels block is verticallysplit into two N pixels by N pixels sub blocks in step (1), and the leftN pixels by N pixels block is vertically split into two N/2 pixels by Npixels sub blocks in step (2). In step (3), a current block can bepartitioned into three sub blocks using a partition mode selected for aN pixels by N pixels current block (the left block in this example), asillustrated in (c) and (f) in FIG. 26 . The sizes of the three subblocks may be different. For example, among the three sub blocks, alarge sub block may have two times the width/height of a small subblock. Furthermore, for example, the selected partition mode can splitthe current block into two sub blocks with different sizes (asymmetricalbinary tree) as illustrated in (a), (b), (d), and (e) in FIG. 26 . Forexample, when an asymmetrical binary tree is used, the large sub blockcan have three times the width/height of the small sub block.

FIG. 27 illustrates an example of partitioning a N pixels by N pixelsblock using a partition mode selected when the second partition mode isnot to be selected, as illustrated in step (3), in Embodiment 2. Asillustrated in FIG. 27 , a N pixels by 2N pixels block is horizontallysplit into two N pixels by N pixels sub blocks in step (1), and the topN pixels by N pixels block is horizontally split into two N pixels byN/2 pixels sub blocks in step (2). In step (3), a current block can bepartitioned into three sub blocks using a partition mode selected for aN pixels by N pixels current block (the bottom block in this example),as illustrated in (c) and (f) in FIG. 27 . The sizes of the three subblocks may be different. For example, among the three sub blocks, alarge sub block may have two times the width/height of a small subblock. Furthermore, for example, the selected partition mode can splitthe current block into two sub blocks with different sizes (asymmetricalbinary tree) as illustrated in (a), (b), (d), and (e) in FIG. 27 . Forexample, when an asymmetrical binary tree is used, the large sub blockcan have three times the width/height of the small sub block.

FIG. 17 illustrates the possible locations of the first parameter in acompressed video bitstream. As illustrated in FIG. 17 , the firstparameter can be in a video parameter set, a sequence parameter set, apicture parameter set, a slice header, or a coding tree unit. The firstparameter can indicate the way for partitioning a block into a pluralityof sub blocks. For example, the first parameter can include a flag toindicate whether the block is to be partitioned in horizontal orvertical direction. The first parameter can also include a parameter toindicate whether the block is to be partitioned into two or more subblocks.

FIG. 18 illustrates the possible locations of the second parameter in acompressed video bitstream. As illustrated in FIG. 18 , the secondparameter can be in a video parameter set, a sequence parameter set, apicture parameter set, a slice header, or a coding tree unit. The secondparameter can indicate the way for partitioning a block into a pluralityof sub blocks. For example, the second parameter can include a flag toindicate whether the block is to be partitioned in a horizontal orvertical direction. The second parameter can also include a parameter toindicate whether the block is to be partitioned into two or more subblocks. The second parameter follows after the first parameter in abitstream as illustrated in FIG. 19 .

The first block and the second block are different blocks. The firstblock and the second block can be included in the same frame. Forexample, the first block may be the top neighboring block to the secondblock. Furthermore, for example, the first block may be the leftneighboring block to the second block.

In step S1007, the second block is partitioned into sub blocks using theselected partition mode. In step S1008, the partitioned blocks areencoded.

[Encoder]

FIG. 15 is a block diagram illustrating the structure of a video/imageencoder according to Embodiment 2 or 3.

Video encoder 5000 is an apparatus for encoding an input video/image ona block-by-block basis so as to generate an encoded output bit stream.As illustrated in FIG. 15 , video encoder 5000 includes transformer5001, quantizer 5002, inverse quantizer 5003, inverse transformer 5004,block memory 5005, frame memory 5006, intra predictor 5007, interpredictor 5008, entropy encoder 5009, and block partition determiner5010.

An input video is inputted to an adder, and the added value is outputtedto transformer 5001. Transformer 5001 transforms the added values intofrequency coefficients based on the block partition mode derived fromblock partition determiner 5010, and outputs the frequency coefficientsto quantizer 5002. The block partition mode can be related to a blockpartition mode, a block partition type, or a block partition direction.Quantizer 5002 quantizes the inputted quantized coefficients, andoutputs the quantized values to inverse quantizer 5003 and entropyencoder 5009.

Inverse quantizer 5003 inversely quantizes the quantized valuesoutputted from quantizer 5002, and outputs the frequency coefficients toinverse transformer 5004. Inverse transformer 5004 performs inversefrequency transform on the frequency coefficients based on the blockpartition mode derived from block partition determiner 5010, so as totransform the frequency coefficients into sample values of the bitstream, and outputs the sample values to an adder.

The adder adds the sample values of the bit stream outputted frominverse transformer 5004 to the predicted video/image values outputtedfrom inter/intra predictor 5007, 5008, and outputs the added values toblock memory 5005 or frame memory 5006 for further prediction. Blockpartition determiner 5010 collects block information from block memory5005 or frame memory 5006 to derive a block partition mode andparameters related to the block partition mode. Using the derived blockpartition mode will result in partitioning a block into a plurality ofsub blocks. Inter/intra predictor 5007, 5008 searches withinvideos/images stored in block memory 5005 or from videos/images in framememory 5006 reconstructed using the block partition mode derived fromblock partition determiner 5010, and estimates a video/image area whichis for example most similar to the input videos/images for prediction.

Entropy encoder 5009 encodes the quantized values outputted fromquantizer 5002, encodes parameters from block partition determiner 5010,and outputs a bit stream.

[Decoding Process]

FIG. 12 illustrates a video decoding process according to Embodiment 2.

First, in step S2001, a first parameter for identifying, from aplurality of partition modes, a partition mode for partitioning a firstblock into sub blocks is parsed from a bitstream. Using a partition modewill result in partitioning a block into sub blocks, and using differentpartition modes can result in partitioning a block into sub blocks withdifferent shapes, or different heights, or different widths.

FIG. 28 illustrates examples of partition modes for partitioning a Npixels by N pixels block in Embodiment 2. In FIG. 28 , (a) to (h) showdifferent partition modes. As illustrated in FIG. 28 , using partitionmode (a) will partition a N pixels by N pixels block (value of ‘N’ canbe any value in the range from 8 to 128 which are integer multiples of4, for example a 16 pixels by 16 pixels block) into two N/2 pixels by Npixels sub blocks (for example, 8 pixels by 16 pixels sub blocks). Usingpartition mode (b) will partition a N pixels by N pixels block into aN/4 pixels by N pixels sub block and a 3N/4 pixels by N pixels sub block(for example, a 4 pixels by 16 pixels sub block and a 12 pixels by 16pixels sub block). Using partition mode (c) will partition a N pixels byN pixels block into a 3N/4 pixels by N pixels sub block and a N/4 pixelsby N pixels sub block (for example, a 12 pixels by 16 pixels sub blockand a 4 pixels by 16 pixels sub block). Using partition mode (d) willpartition a N pixels by N pixels block into a N/4 pixels by N pixels subblock, a N/2 pixels by N pixels sub block, and a N/4 pixels by N pixelssub block (for example, a 4 pixels by 16 pixels sub block, a 8 pixels by16 pixels sub block and a 4 pixels by 16 pixels sub block). Usingpartition mode (e) will partition a N pixels by N pixels block into twoN pixels by N/2 pixels sub blocks (for example, 16 pixels by 8 pixelssub blocks). Using partition mode (f) will partition a N pixels by Npixels block into a N pixels by N/4 pixels sub block and a N pixels by3N/4 pixels sub block (for example, a 16 pixels by 4 pixels sub blockand a 16 pixels by 12 pixels sub block). Using partition mode (g) willpartition a N pixels by N pixels block into a N pixels by 3N/4 pixelssub block and a N pixels by N/4 pixels sub block (for example, a 16pixels by 12 pixels sub block and a 16 pixels by 4 pixels sub block).Using partition mode (h) will partition a N pixels by N pixels blockinto a N pixels by N/4 pixels sub block, a N pixels by N/2 pixels subblock, and a N pixels by N/4 pixels sub block (for example, a 16 pixelsby 4 pixels sub block, a 16 pixels by 8 pixels sub block and a 16 pixelsby 4 pixels sub block).

Next, in step S2002, it is determined whether a first parameteridentifies a first partition mode.

Next, in step S2003, based on at least the determination as to whetherthe first parameter identified a first partition mode, it is determinedif second partition mode is not to be selected as a candidate forpartitioning a second block.

The two different sets of partition modes may partition a block into subblocks of the same shapes and sizes. For example, as illustrated in FIG.31A, sub blocks from (1 b) and (2 c) have same shapes and sizes. A setof partition modes can include at least two partition modes. Forexample, a set of partition modes can include a ternary tree verticalsplit followed by a binary tree vertical split on the center sub blockand no split on other sub blocks as illustrated in (1 a) and (1 b) inFIG. 31A. Furthermore, for example, another set of partition modes caninclude a binary tree vertical split followed by a binary tree verticalsplit on both of the sub blocks, as illustrated in (2 a), (2 b), and (2c) in FIG. 31A. Both sets of partition modes will result in sub blocksof same shapes and sizes.

When selecting among two sets of partition modes that result insplitting a block into sub blocks of same shapes and sizes and each setsof partition modes, when encoded in a bit stream, have different numberof bins or different number of bits, the set of partition modes that hasfewer number of bins or fewer number of bits is selected among the twosets.

When selecting among two sets of partition modes that result insplitting a block into sub blocks of same shapes and sizes and each setsof partition modes, when encoded in a bit stream, have the same numberof bins or same number of bits, the set of partition modes that appearsfirst in a predetermined order of a plurality of sets of partition modesis selected among the two sets. An example of the predetermined ordermay be an order based on the number of partition modes in each set ofpartition modes.

FIG. 31A and FIG. 31B illustrate an example of splitting a block intosub blocks using a set of partition modes with fewer bins in theencoding partition modes. In this example, when the left N pixels by Npixels block is vertically split into two sub blocks, the secondpartition mode in step (2c), for the right N pixels by N pixels block isnot selected. This is because, in the partition mode encoding method inFIG. 31B, the second set of partition modes (2 a, 2 b, 2 c) will requiremore bins from encoding partition modes as compared to the first set ofpartition modes (1 a, 1 b).

FIG. 32A illustrates an example of splitting a block into sub blocksusing a set of partition modes that appears first in a predeterminedorder of a plurality of sets of partition modes. In this example, whenthe top 2N pixels by N/2 pixels block is vertically split into three subblocks, the second partition mode in step (2c), for the bottom 2N pixelsby N/2 pixels block is not selected. This is because, in the partitionmode encoding method in FIG. 32B, the second set of partition modes (2a, 2 b, 2 c) has the same number of bins as the first set of partitionmodes (1 a, 1 b, 1 c, 1 d) and appears after the first set of partitionmodes (1 a, 1 b, 1 c, 1 d) in the predetermined order of sets ofpartitions modes in FIG. 32C. The predetermined order of the pluralitysets of partition modes can be fixed or signalled in a bitstream.

FIG. 20 illustrates an example in which a second partition mode is notselected for partitioning a 2N pixels by N pixels block, as illustratedin step (2c), in Embodiment 1. As illustrated in FIG. 20 , a 2N pixelsby 2N pixels block (for example, a 16 pixels by 16 pixels block) can besplit into four equal sub blocks of size N pixels by N pixels (forexample, 8 pixels by 8 pixels) using a first way of splitting (i), as instep (1a). Furthermore, a 2N pixels by 2N pixels block can also be splitinto two equal sub blocks of size 2N pixels by N pixels (for example, 16pixels by 8 pixels) using a second way of splitting (2 a), as in step(2a). During the second way of splitting (ii), when first partition modesplits the top 2N pixels by N pixels block (first block) vertically intotwo N pixels by N pixels sub blocks as in step (2b), the secondpartition mode which vertically splits the bottom 2N pixels by N pixelsblock (second block) into two N pixels by N pixels sub blocks in step(2c) is not selected as a candidate for possible partition mode. This isbecause the second partition mode will produce sub blocks sizes same asthe quad split sub block sizes from the first way of splitting (i).

In this manner, in FIG. 20 , when the first block is vertically splitinto two equal sub blocks if the first partition mode is used, and thesecond block vertically neighboring the first block is vertically splitinto two equal sub blocks if the second partition mode is used, thesecond partition mode is not selected as a candidate.

FIG. 21 illustrates an example in which a second partition mode is notselected for partitioning a N pixels by 2N pixels block, as illustratedin step (2c), in Embodiment 2. As illustrated in FIG. 21 , a 2N pixelsby 2N pixels block can be split into four equal sub blocks of N pixelsby N pixels using the first way of splitting (i). Furthermore, as instep (2a), a 2N pixels by 2N pixels block can also be vertically splitinto two equal sub blocks of N pixels by 2N pixels (for example, 8pixels by 16 pixels) using the second way of splitting (ii). During thesecond way of splitting (ii), when first partition mode splits the leftN pixels by 2N pixels block (first block) horizontally into two N pixelsby N pixels sub blocks as in step (2b), the second partition mode whichhorizontally splits the right N pixels by 2N pixels block (second block)into two N pixels by N pixels sub blocks in step (2c) is not selected asa candidate for possible partition mode. This is because the secondpartition mode will produce sub blocks sizes same as the quad split subblock sizes from the first way of splitting (i).

In this manner, in FIG. 21 , when the first block is horizontally splitinto two equal sub blocks if the first partition mode is used, and thesecond block horizontally neighboring the first block is horizontallysplit into two equal sub blocks if the second partition mode is used,the second partition mode is not selected as a candidate.

FIG. 22 illustrates an example in which a second partition mode is notselected for partitioning a N pixels by N pixels block, as illustratedin step (2c), in Embodiment 2. As illustrated in FIG. 22 , a 2N pixelsby N pixels (value of ‘N’ can be any value in the range from 8 to 128which are integer multiples of 4, for example, 16 pixels by 8 pixels)block can be split vertically into a N/2 pixels by N pixels sub block, aN pixels by N pixels sub block, and a N/2 pixels by N pixels sub block(for example, a 4 pixels by 8 pixels sub block, a 8 pixels by 8 pixelssub block, a 4 pixels by 8 pixels sub block), using the first way ofsplitting (i), as in step (1a). Furthermore, a 2N pixels by N pixelsblock can also be split into two N pixels by N pixels sub blocks usingthe second way of splitting (ii), as in step (2a). During the first wayof splitting (i), the center N pixels by N pixels block can bevertically split into two N/2 pixels by N pixels (for example, 4 pixelsby 8 pixels) sub blocks in step (1b). During the second way of splitting(ii), when the left N pixels by N pixels block (first block) isvertically split into two N/2 pixels by N pixels sub blocks as in step(2b), a partition mode which vertically splits the right N pixels by Npixels block (second block) into two N/2 pixels by N pixels sub blocksin step (2c) is not selected as a candidate for possible partition mode.This is because, the partition mode will produce sub blocks sizes whichare the same as that obtained from the first way of splitting (i), orfour N/2 pixels by N pixels sub blocks.

In this manner, in FIG. 22 , when the first block is vertically splitinto two equal sub blocks if the first partition mode is used, and thesecond block horizontally neighboring the first block is verticallysplit into two equal sub blocks if the second partition mode is used,the second partition mode is not selected as a candidate.

FIG. 23 illustrates an example in which a second partition mode is notselected for partitioning a N pixels by N pixels block, as illustratedin step (2c), in Embodiment 2. As illustrated in FIG. 23 , a N pixels by2N pixels (value of ‘N’ can be any value in the range from 8 to 128which are integer multiples of 4, for example, 8 pixels by 16 pixels)block can be split into a N pixels by N/2 pixels sub block, a N pixelsby N pixels sub block, and a N pixels by N/2 pixels sub block (forexample, a 8 pixels by 4 pixels sub block, a 8 pixels by 8 pixels subblock, a 8 pixels by 4 pixels sub block) using the first way ofsplitting (i), as in step (1a). Furthermore, a N pixels by 2N pixelsblock can also be split into two N pixels by N pixels sub blocks usingthe second way of splitting, as in step (2a). During the first way ofsplitting (i), the center N pixels by N pixels block can be horizontallysplit into two N pixels by N/2 pixels sub blocks, as in step (1b).During the second way of splitting (ii), when the top N pixels by Npixels (first block) is horizontally split into two N pixels by N/2pixels sub blocks in step (2b), a partition mode which horizontallysplits the bottom N pixels by N pixels (second block) into two N pixelsby N/2 pixels sub blocks in step (2c) is not selected as a candidate forpossible partition mode. This is because, the partition mode willproduce sub blocks sizes which are the same as that obtained from thefirst way of splitting (i), or four N pixels by N/2 pixels sub blocks.

In this manner, in FIG. 23 , when the first block is horizontally splitinto two equal sub blocks if the first partition mode is used, and thesecond block vertically neighboring the first block is horizontallysplit into two equal sub blocks if the second partition mode is used,the second partition mode is not selected as a candidate.

If it is determined that the second partition mode is to be selected asa candidate for partitioning a second block (N in S2003), the secondparameter is parsed from the bitstream and a partition mode is selectedfrom a plurality of partition modes which include the second partitionmode as a candidate in step S2004.

If it is determined that the second partition mode is not to be selectedas a candidate for partitioning the second block (Y in S2003), apartition mode different from the second partition mode is selected forpartitioning the second block in step S2005. Here, the selectedpartition mode partitions a block into sub blocks with different shapesor different sizes as compared to sub blocks that would have beengenerated by the second partition mode.

FIG. 24 illustrates an example of partitioning a 2N pixels by N pixelsblock using a partition mode selected when the second partition mode isnot to be selected, as illustrated in step (3), in Embodiment 2. Asillustrated in FIG. 24 , the selected partition mode can split a current2N pixels by N pixels block (the bottom block in this example) intothree sub blocks as illustrated in (c) and (f) in FIG. 24 . The sizes ofthe three sub blocks may be different. For example, among the three subblocks, a large sub block may have two times the width/height of a smallsub block. Furthermore, for example, the selected partition mode cansplit the current block into two sub blocks with different sizes(asymmetrical binary tree) as illustrated in (a), (b), (d), and (e) inFIG. 24 . For example, when an asymmetrical binary tree is used, thelarge sub block can have three times the width/height of the small subblock.

FIG. 25 illustrates an example of partitioning a N pixels by 2N pixelsblock using a partition mode selected when the second partition mode isnot to be selected, as illustrated in step (3), in Embodiment 2. Asillustrated in FIG. 25 , the selected partition mode can split thecurrent N pixels by 2N pixels block (the right block in this example)into three sub blocks as illustrated in (c) and (f) in FIG. 25 . Thesizes of the three sub blocks may be different. For example, among thethree sub blocks, a large sub block may have two times the width/heightof a small sub block. Furthermore, for example, the selected partitionmode can split the current block into two sub blocks with differentsizes (asymmetrical binary tree) as illustrated in (a), (b), (d), and(e) in FIG. 25 . For example, when an asymmetrical binary tree is used,the large sub block can have three times the width/height of the smallsub block.

FIG. 26 illustrates an example of partitioning a N pixels by N pixelsblock using a partition mode selected when the second partition mode isnot to be selected, as illustrated in step (3), in Embodiment 2. Asillustrated in FIG. 26 , a 2N pixels by N pixels block is verticallysplit into two N pixels by N pixels sub blocks in step (1), and the leftN pixels by N pixels block is vertically split into two N/2 pixels by Npixels sub blocks in step (2). In step (3), a current block can bepartitioned into three sub blocks using a partition mode selected for aN pixels by N pixels current block (the left block in this example), asillustrated in (c) and (f) in FIG. 26 . The sizes of the three subblocks may be different. For example, among the three sub blocks, alarge sub block may have two times the width/height of a small subblock. Furthermore, for example, the selected partition mode can splitthe current block into two sub blocks with different sizes (asymmetricalbinary tree) as illustrated in (a), (b), (d), and (e) in FIG. 26 . Forexample, when an asymmetrical binary tree is used, the large sub blockcan have three times the width/height of the small sub block.

FIG. 27 illustrates an example of partitioning a N pixels by N pixelsblock using a partition mode selected when the second partition mode isnot to be selected, as illustrated in step (3), in Embodiment 2. Asillustrated in FIG. 27 , a N pixels by 2N pixels block is horizontallysplit into two N pixels by N pixels sub blocks in step (1), and the topN pixels by N pixels block is horizontally split into two N pixels byN/2 pixels sub blocks in step (2). In step (3), a current block can bepartitioned into three sub blocks using a partition mode selected for aN pixels by N pixels current block (the bottom block in this example),as illustrated in (c) and (f) in FIG. 27 . The sizes of the three subblocks may be different. For example, among the three sub blocks, alarge sub block may have two times the width/height of a small subblock. Furthermore, for example, the selected partition mode can splitthe current block into two sub blocks with different sizes (asymmetricalbinary tree) as illustrated in (a), (b), (d), and (e) in FIG. 27 . Forexample, when an asymmetrical binary tree is used, the large sub blockcan have three times the width/height of the small sub block.

FIG. 17 illustrates the possible locations of the first parameter in acompressed video bitstream. As illustrated in FIG. 17 , the firstparameter can be in a video parameter set, a sequence parameter set, apicture parameter set, a slice header, or a coding tree unit. The firstparameter can indicate the way for partitioning a block into a pluralityof sub blocks. For example, the first parameter can include a flag toindicate whether the block is to be partitioned in a horizontal orvertical direction. The first parameter can also include a parameter toindicate whether the block is to be partitioned into two or more subblocks.

FIG. 18 illustrates the possible locations of the second parameter in acompressed video bitstream. As illustrated in FIG. 18 , the secondparameter can be in a video parameter set, a sequence parameter set, apicture parameter set, a slice header, or a coding tree unit. The secondparameter can indicate the way for partitioning a block into a pluralityof sub blocks. For example, the second parameter can include a flag toindicate whether the block is to be partitioned in a horizontal orvertical direction. The second parameter can also include a parameter toindicate whether the block is to be partitioned into two or more subblocks. The second parameter follows after the first parameter in abitstream as illustrated in FIG. 19 .

The first block and the second block are different blocks. The firstblock and the second block may be included in the same frame. Forexample, the first block may be the top neighboring block to the secondblock. Furthermore, for example, the first block may be the leftneighboring block to the second block.

In step S2006, the second block is partitioned into sub blocks using theselected partition mode. In step S2007, the partitioned blocks aredecoded.

[Decoder]

FIG. 16 is a block diagram illustrating the structure of a video/imagedecoder according to Embodiment 2 or 3.

Video decoder 6000 is an apparatus for decoding an input coded bitstream on a block-by-block basis and outputting videos/images. Asillustrated in FIG. 16 , video decoder 6000 includes entropy decoder6001, inverse quantizer 6002, inverse transformer 6003, block memory6004, frame memory 6005, intra predictor 6006, inter predictor 6007, andblock partition determiner 6008.

An input encoded bit stream is inputted to entropy decoder 6001. Afterthe input encoded bit stream is inputted to entropy decoder 6001,entropy decoder 6001 decodes the input encoded bit stream, outputsparameters to block partition determiner 6008, and outputs the decodedvalues to inverse quantizer 6002.

Inverse quantizer 6002 inversely quantizes the decoded values, andoutputs the frequency coefficients to inverse transformer 6003. Inversetransformer 6003 performs inverse frequency transform on the frequencycoefficients based on the block partition mode derived from blockpartition determiner 6008 to transform the frequency coefficients intosample values, and outputs the sample values to an adder. The blockpartition mode can be related to a block partition mode, a blockpartition type, or a block partition direction. The adder adds thesample values to the predicted video/image values outputted fromintra/inter predictors 6006, 6007, and outputs the added values to adisplay, and outputs the added values to block memory 6004 or framememory 6005 for further prediction. Block partition determiner 6008collects block information from block memory 6004 or frame memory 6005to derive block partition mode using the parameters decoded by entropydecoder 6001. Using the derived block partition mode will result inpartitioning a block into a plurality of sub blocks. In addition,intra/inter predictor 6006, 6007 estimates a video/image area of theblock to be decoded, from within videos/images stored in block memory6004 or from videos/images in frame memory 6005 reconstructed using theblock partition mode derived from block partition determiner 6008.

Embodiment 3

The encoding process and decoding process according to Embodiment 3 willbe described in detail with reference to FIG. 13 and FIG. 14 . Theencoder and decoder according to Embodiment 3 will be described indetail with reference to FIG. 15 and FIG. 16 .

[Encoding Process]

FIG. 13 illustrates a video encoding process according to Embodiment 3.

First, in step S3001, a first parameter for identifying, from aplurality of partition types, a partition type for partitioning a firstblock into sub blocks is written into a bitstream.

Next, in step S3002, a second parameter indicating the partitiondirection is written into the bitstream. The second parameter followsafter the first parameter in a bitstream. The partition type togetherwith the partition direction may form the partition mode. The partitiontype indicates the number of sub blocks and partition ratio forpartitioning a block.

FIG. 29 illustrates examples of partition types and partition directionsfor partitioning a N pixels by N pixels block in Embodiment 3. In FIG.29 , (1), (2), (3), and (4) are different partition types, (1 a), (2 a),(3 a), and (4 a) are different partition modes from related partitiontypes in vertical partition direction, and (1 b), (2 b), (3 b), and (4b) are different partition modes from related partition types inhorizontal partition direction. As illustrated in FIG. 29 , a N pixelsby N pixels block is partitioned using partition mode (1 a) when it ispartitioned with symmetrical binary tree (i.e., two sub blocks) invertical partition direction with partition ratio 1:1. A N pixels by Npixels block is partitioned using partition mode (1 b) when it ispartitioned with symmetrical binary tree (i.e., two sub blocks) inhorizontal partition direction with partition ratio 1:1. AN pixels by Npixels block is partitioned using partition mode (2 a) when it ispartitioned with asymmetrical binary tree (i.e., two sub blocks) invertical partition direction at partition ratio 1:3. A N pixels by Npixels block is partitioned using partition mode (2 b) when it ispartitioned with asymmetrical binary tree (i.e., two sub blocks) inhorizontal partition direction at partition ratio 1:3. A N pixels by Npixels block is partitioned using partition mode (3 a) when it ispartitioned with asymmetrical binary tree (i.e., two sub blocks) invertical partition direction at partition ratio 3:1. A N pixels by Npixels block is partitioned using partition mode (3 b) when it ispartitioned with asymmetrical binary tree (i.e., two sub blocks) inhorizontal partition direction at partition ratio 3:1. A N pixels by Npixels block is partitioned using partition mode (4 a) when it ispartitioned with ternary tree (i.e., three sub blocks) in verticalpartition direction at partition ratio 1:2:1. AN pixels by N pixelsblock is partitioned using partition mode (4 b) when it is partitionedwith ternary tree (or three sub blocks) in horizontal partitiondirection at partition ratio 1:2:1.

FIG. 17 illustrates the possible locations of the first parameter in acompressed video bitstream. As illustrated in FIG. 17 , the firstparameter can be in a video parameter set, a sequence parameter set, apicture parameter set, a slice header, or a coding tree unit. The firstparameter can indicate the way for partitioning a block into a pluralityof sub blocks. For example, the first parameter can include a flag toindicate whether the block is to be partitioned in a horizontal orvertical direction. The first parameter can also include a parameter toindicate whether the block is to be partitioned into two or more subblocks.

FIG. 18 illustrates the possible locations of the second parameter in acompressed video bitstream. As illustrated in FIG. 18 , the secondparameter can be in video parameter set, sequence parameter set, pictureparameter set, slice header, or coding tree unit. The second parametercan indicate the way for partitioning a block into a plurality of subblocks. For example, the second parameter can include a flag to indicatewhether the block is to be partitioned in a horizontal or verticaldirection. The second parameter can also include a parameter to indicatewhether the block is to be partitioned into two or more sub blocks. Thesecond parameter follows after the first parameter in a bitstream asillustrated in FIG. 19 .

FIG. 30 illustrates an advantage of encoding partition type beforepartition direction as compared to encoding partition direction beforepartition type. In this example, when horizontal partition direction isdisabled due to unsupported size (16 pixels by 2 pixels), there is noneed to encode partition direction. Partition direction is determined asvertical partition direction as horizontal partition direction isdisabled in this example. Encoding partition type before partitiondirection saves coding bits from encoding partition direction ascompared to encoding partition direction before partition type.

In this manner, it is possible to determine whether a block can bepartitioned in each of the horizontal direction and vertical directionbased on a predetermined condition for allowed or not-allowed blockpartitioning. Then, when it is determined that partitioning is possiblein only one of the horizontal direction and the vertical direction,writing of the partition direction into a bitstream can be skipped. Inaddition, when it is determined that it partitioning is not possible inboth the horizontal direction and the vertical direction, in addition tothe partition direction, writing of the partition type into thebitstream may also be skipped.

The predetermined condition for allowed or not-allowed blockpartitioning is defined by the size (number of pixels) or the number oftimes partitioning is performed, for example. The condition for allowedor not-allowed block partitioning may be predefined in a standardspecification. Furthermore, the condition for allowed or not-allowedblock partitioning may be included in a video parameter set, a sequenceparameter set, a picture parameter set, a slice header, or a coding treeunit. The condition for allowed or not-allowed block partitioning may befixed for all blocks, and may be dynamically switched according to ablock property (for example, luma and chroma block) or a pictureproperty (for example, I, P, and B picture)

In step S3003, the block is partitioned into sub blocks using theidentified partition type and the indicated partition direction. In stepS3004, the partitioned blocks are encoded.

[Encoder]

FIG. 15 is a block diagram illustrating the structure of a video/imageencoder according to Embodiment 2 or 3.

Video encoder 5000 is an apparatus for encoding an input video/image ona block-by-block basis so as to generate an encoded output bit stream.As illustrated in FIG. 15 , video encoder 5000 includes transformer5001, quantizer 5002, inverse quantizer 5003, inverse transformer 5004,block memory 5005, frame memory 5006, intra predictor 5007, interpredictor 5008, entropy encoder 5009, and block partition determiner5010.

An input video is inputted to an adder, and the added value is outputtedto transformer 5001. Transformer 5001 transforms the added values intofrequency coefficients based on the block partition type and directionderived from block partition determiner 5010, and outputs the frequencycoefficients to quantizer 5002. The block partition type and directioncan be related to a block partition mode, a block partition type, or ablock partition direction. Quantizer 5002 quantizes the inputtedquantized coefficients, and outputs the quantized values to inversequantizer 5003 and entropy encoder 5009.

Inverse quantizer 5003 inversely quantizes the quantized valuesoutputted from quantizer 5002, and outputs the frequency coefficients toinverse transformer 5004. Inverse transformer 5004 performs inversefrequency transform on the frequency coefficients based on the blockpartition type and direction derived from block partition determiner5010, so as to transform the frequency coefficients into sample valuesof the bit stream, and outputs the sample values to an adder.

The adder adds the sample values of the bit stream outputted frominverse transformer 5004 to the predicted video/image values outputtedfrom inter/intra predictor 5007, 5008, and outputs the added values toblock memory 5005 or frame memory 5006 for further prediction. Blockpartition determiner 5010 collects block information from block memory5005 or frame memory 5006 to derive a block partition type and directionand parameters related to the block partition type and direction. Usingthe derived block partition type and direction will result inpartitioning a block into a plurality of sub blocks. Inter/intrapredictor 5007, 5008 searches within videos/images stored in blockmemory 5005 or from videos/images in frame memory 5006 reconstructedusing the block partition type and direction derived from blockpartition determiner 5010, and estimates a video/image area which is forexample most similar to the input videos/images for prediction.

Entropy encoder 5009 encodes the quantized values outputted fromquantizer 5002, encodes parameters from block partition determiner 5010,and outputs a bit stream.

[Decoding Process]

FIG. 14 illustrates a video decoding process according to Embodiment 3.

First, in step S4001, a first parameter for identifying, from aplurality of partition types, a partition type for partitioning a firstblock into sub blocks is parsed from a bitstream.

Next, in step S4002, a second parameter indicating partition directionis parsed from the bitstream. The second parameter follows after thefirst parameter in a bitstream. The partition type together with thepartition direction may form the partition mode. The partition typeindicates the number of sub blocks and partition ratio for partitioninga block.

FIG. 29 illustrates examples of partition types and partition directionsfor partitioning a N pixels by N pixels block in Embodiment 3. In FIG.29 , (1), (2), (3), and (4) are different partition types, (1 a), (2 a),(3 a), and (4 a) are different partition modes from related partitiontypes in vertical partition direction, and (1 b), (2 b), (3 b), and (4b) are different partition modes from related partition types inhorizontal partition direction. As illustrated in FIG. 29 , a N pixelsby N pixels block is partitioned using partition mode (1 a) when it ispartitioned with symmetrical binary tree (i.e., two sub blocks) invertical partition direction with partition ratio 1:1. A N pixels by Npixels block is partitioned using partition mode (1 b) when it ispartitioned with symmetrical binary tree (i.e., two sub blocks) inhorizontal partition direction with partition ratio 1:1. AN pixels by Npixels block is partitioned using partition mode (2 a) when it ispartitioned with asymmetrical binary tree (i.e., two sub blocks) invertical partition direction at partition ratio 1:3. A N pixels by Npixels block is partitioned using partition mode (2 b) when it ispartitioned with asymmetrical binary tree (i.e., two sub blocks) inhorizontal partition direction at partition ratio 1:3. A N pixels by Npixels block is partitioned using partition mode (3 a) when it ispartitioned with asymmetrical binary tree (i.e., two sub blocks) invertical partition direction at partition ratio 3:1. A N pixels by Npixels block is partitioned using partition mode (3 b) when it ispartitioned with asymmetrical binary tree (i.e., two sub blocks) inhorizontal partition direction at partition ratio 3:1. A N pixels by Npixels block is partitioned using partition mode (4 a) when it ispartitioned with ternary tree (i.e., three sub blocks) in verticalpartition direction at partition ratio 1:2:1. AN pixels by N pixelsblock is partitioned using partition mode (4 b) when it is partitionedwith ternary tree (or three sub blocks) in horizontal partitiondirection at partition ratio 1:2:1.

FIG. 17 illustrates the possible locations of the first parameter in acompressed video bitstream. As illustrated in FIG. 17 , the firstparameter can be in video parameter set, sequence parameter set, pictureparameter set, slice header, or coding tree unit. The first parametercan indicate the way for partitioning a block into a plurality of subblocks. For example, the first parameter can include an identifier ofthe aforementioned partition type. For example, the first parameter caninclude a flag to indicate whether the block is to be partitioned in ahorizontal or vertical direction. The first parameter can also include aparameter to indicate whether the block is to be partitioned into two ormore sub blocks.

FIG. 18 illustrates the possible locations of the second parameter in acompressed video bitstream. As illustrated in FIG. 18 , the secondparameter can be in video parameter set, sequence parameter set, pictureparameter set, slice header, or coding tree unit. The second parametercan indicate the way for partitioning a block into a plurality of subblocks. For example, the second parameter can include a flag to indicatewhether the block is to be partitioned in a horizontal or verticaldirection. Specifically, the second parameter can include a parameter toindicate the partition direction. The second parameter can also includea parameter to indicate whether the block is to be partitioned into twoor more sub blocks. The second parameter follows after the firstparameter in a bitstream as illustrated in FIG. 19 .

FIG. 30 illustrates an advantage of encoding partition type beforepartition direction as compared to encoding partition direction beforepartition type. In this example, when horizontal partition direction isdisabled due to unsupported size (16 pixels by 2 pixels), there is noneed to encode partition direction. Partition direction is determined asvertical partition direction as horizontal partition direction isdisabled in this example. Encoding partition type before partitiondirection saves coding bits from encoding partition direction ascompared to encoding partition direction before partition type.

In this manner, it is possible to determine whether a block can bepartitioned in each of the horizontal direction and vertical directionbased on a predetermined condition for allowed or not-allowed blockpartitioning. Then, when it is determined that partitioning is possiblein only one of the horizontal direction and the vertical direction,parsing of the partition direction from a bitstream can be skipped. Inaddition, when it is determined that it partitioning is not possible inboth the horizontal direction and the vertical direction, in addition tothe partition direction, parsing of the partition type from thebitstream may also be skipped.

The predetermined condition for allowed or not-allowed blockpartitioning is defined by the size (number of pixels) or the number ortimes partitioning is performed, for example. This condition for allowedor not-allowed block partitioning may be predefined in a standardspecification. Furthermore, the condition for allowed or not-allowedblock partitioning may be included in a video parameter set, a sequenceparameter set, a picture parameter set, a slice header, or a coding treeunit. The condition for allowed or not-allowed block partitioning may befixed for all blocks, and may be dynamically switched according to ablock property (for example, luma and chroma block) or a pictureproperty (for example, I, P, and B picture)

In step S4003, the block is partitioned into sub blocks using theidentified partition type and the indicated partition direction. In stepS4004, the partitioned blocks are decoded.

[Decoder]

FIG. 16 is a block diagram illustrating the structure of a video/imagedecoder according to Embodiment 2 or 3.

Video decoder 6000 is an apparatus for decoding an input coded bitstream on a block-by-block basis and outputting videos/images. Asillustrated in FIG. 16 , video decoder 6000 includes entropy decoder6001, inverse quantizer 6002, inverse transformer 6003, block memory6004, frame memory 6005, intra predictor 6006, inter predictor 6007, andblock partition determiner 6008.

An input encoded bit stream is inputted to entropy decoder 6001. Afterthe input encoded bit stream is inputted to entropy decoder 6001,entropy decoder 6001 decodes the input encoded bit stream, outputsparameters to block partition determiner 6008, and outputs the decodedvalues to inverse quantizer 6002.

Inverse quantizer 6002 inversely quantizes the decoded values, andoutputs the frequency coefficients to inverse transformer 6003. Inversetransformer 6003 performs inverse frequency transform on the frequencycoefficients based on the block partition type and direction derivedfrom block partition determiner 6008 to transform the frequencycoefficients into sample values, and outputs the sample values to anadder. The block partition type and direction can be related to a blockpartition mode, a block partition type, or a block partition direction.The adder adds the sample values to the predicted video/image valuesoutputted from intra/inter predictors 6006, 6007, and outputs the addedvalues to a display, and outputs the added values to block memory 6004or frame memory 6005 for further prediction. Block partition determiner6008 collects block information from block memory 6004 or frame memory6005 to derive block partition type and direction using the parametersdecoded by entropy decoder 6001. Using the derived block partition typeand direction will result in partitioning a block into a plurality ofsub blocks. In addition, intra/inter predictor 6006, 6007 estimates avideo/image area of the block to be decoded, from within videos/imagesstored in block memory 6004 or from videos/images in frame memory 6005reconstructed using the block partition type and direction derived fromblock partition determiner 6008.

Embodiment 4

As described in each of the above embodiments, each functional block cantypically be realized as an MPU and memory, for example. Moreover,processes performed by each of the functional blocks are typicallyrealized by a program execution unit, such as a processor, reading andexecuting software (a program) recorded on a recording medium such asROM. The software may be distributed via, for example, downloading, andmay be recorded on a recording medium such as semiconductor memory anddistributed. Note that each functional block can, of course, also berealized as hardware (dedicated circuit).

Moreover, the processing described in each of the embodiments may berealized via integrated processing using a single apparatus (system),and, alternatively, may be realized via decentralized processing using aplurality of apparatuses. Moreover, the processor that executes theabove-described program may be a single processor or a plurality ofprocessors. In other words, integrated processing may be performed, and,alternatively, decentralized processing may be performed.

Embodiments of the present disclosure are not limited to the aboveexemplary embodiments; various modifications may be made to theexemplary embodiments, the results of which are also included within thescope of the embodiments of the present disclosure.

Next, application examples of the moving picture encoding method (imageencoding method) and the moving picture decoding method (image decodingmethod) described in each of the above embodiments and a system thatemploys the same will be described. The system is characterized asincluding an image encoder that employs the image encoding method, animage decoder that employs the image decoding method, and an imageencoder/decoder that includes both the image encoder and the imagedecoder. Other configurations included in the system may be modified ona case-by-case basis.

Usage Examples

FIG. 33 illustrates an overall configuration of content providing systemex100 for implementing a content distribution service. The area in whichthe communication service is provided is divided into cells of desiredsizes, and base stations ex106, ex107, ex108, ex109, and ex110, whichare fixed wireless stations, are located in respective cells.

In content providing system ex100, devices including computer ex111,gaming device ex112, camera ex113, home appliance ex114, and smartphoneex115 are connected to internet ex101 via internet service providerex102 or communications network ex104 and base stations ex106 throughex110. Content providing system ex100 may combine and connect anycombination of the above elements. The devices may be directly orindirectly connected together via a telephone network or near fieldcommunication rather than via base stations ex106 through ex110, whichare fixed wireless stations. Moreover, streaming server ex103 isconnected to devices including computer ex111, gaming device ex112,camera ex113, home appliance ex114, and smartphone ex115 via, forexample, internet ex101. Streaming server ex103 is also connected to,for example, a terminal in a hotspot in airplane ex117 via satelliteex116.

Note that instead of base stations ex106 through ex110, wireless accesspoints or hotspots may be used. Streaming server ex103 may be connectedto communications network ex104 directly instead of via internet ex101or internet service provider ex102, and may be connected to airplaneex117 directly instead of via satellite ex116.

Camera ex113 is a device capable of capturing still images and video,such as a digital camera. Smartphone ex115 is a smartphone device,cellular phone, or personal handyphone system (PHS) phone that canoperate under the mobile communications system standards of the typical2G, 3G, 3.9G, and 4G systems, as well as the next-generation 5G system.

Home appliance ex118 is, for example, a refrigerator or a deviceincluded in a home fuel cell cogeneration system.

In content providing system ex100, a terminal including an image and/orvideo capturing function is capable of, for example, live streaming byconnecting to streaming server ex103 via, for example, base stationex106. When live streaming, a terminal (e.g., computer ex111, gamingdevice ex112, camera ex113, home appliance ex114, smartphone ex115, orairplane ex117) performs the encoding processing described in the aboveembodiments on still-image or video content captured by a user via theterminal, multiplexes video data obtained via the encoding and audiodata obtained by encoding audio corresponding to the video, andtransmits the obtained data to streaming server ex103. In other words,the terminal functions as the image encoder according to one aspect ofthe present disclosure.

Streaming server ex103 streams transmitted content data to clients thatrequest the stream. Client examples include computer ex111, gamingdevice ex112, camera ex113, home appliance ex114, smartphone ex115, andterminals inside airplane ex117, which are capable of decoding theabove-described encoded data. Devices that receive the streamed datadecode and reproduce the received data. In other words, the devices eachfunction as the image decoder according to one aspect of the presentdisclosure.

[Decentralized Processing]

Streaming server ex103 may be realized as a plurality of servers orcomputers between which tasks such as the processing, recording, andstreaming of data are divided. For example, streaming server ex103 maybe realized as a content delivery network (CDN) that streams content viaa network connecting multiple edge servers located throughout the world.In a CDN, an edge server physically near the client is dynamicallyassigned to the client. Content is cached and streamed to the edgeserver to reduce load times. In the event of, for example, some kind ofan error or a change in connectivity due to, for example, a spike intraffic, it is possible to stream data stably at high speeds since it ispossible to avoid affected parts of the network by, for example,dividing the processing between a plurality of edge servers or switchingthe streaming duties to a different edge server, and continuingstreaming.

Decentralization is not limited to just the division of processing forstreaming; the encoding of the captured data may be divided between andperformed by the terminals, on the server side, or both. In one example,in typical encoding, the processing is performed in two loops. The firstloop is for detecting how complicated the image is on a frame-by-frameor scene-by-scene basis, or detecting the encoding load. The second loopis for processing that maintains image quality and improves encodingefficiency. For example, it is possible to reduce the processing load ofthe terminals and improve the quality and encoding efficiency of thecontent by having the terminals perform the first loop of the encodingand having the server side that received the content perform the secondloop of the encoding. In such a case, upon receipt of a decodingrequest, it is possible for the encoded data resulting from the firstloop performed by one terminal to be received and reproduced on anotherterminal in approximately real time. This makes it possible to realizesmooth, real-time streaming.

In another example, camera ex113 or the like extracts a feature amountfrom an image, compresses data related to the feature amount asmetadata, and transmits the compressed metadata to a server. Forexample, the server determines the significance of an object based onthe feature amount and changes the quantization accuracy accordingly toperform compression suitable for the meaning of the image. Featureamount data is particularly effective in improving the precision andefficiency of motion vector prediction during the second compressionpass performed by the server. Moreover, encoding that has a relativelylow processing load, such as variable length coding (VLC), may behandled by the terminal, and encoding that has a relatively highprocessing load, such as context-adaptive binary arithmetic coding(CABAC), may be handled by the server.

In yet another example, there are instances in which a plurality ofvideos of approximately the same scene are captured by a plurality ofterminals in, for example, a stadium, shopping mall, or factory. In sucha case, for example, the encoding may be decentralized by dividingprocessing tasks between the plurality of terminals that captured thevideos and, if necessary, other terminals that did not capture thevideos and the server, on a per-unit basis. The units may be, forexample, groups of pictures (GOP), pictures, or tiles resulting fromdividing a picture. This makes it possible to reduce load times andachieve streaming that is closer to real-time.

Moreover, since the videos are of approximately the same scene,management and/or instruction may be carried out by the server so thatthe videos captured by the terminals can be cross-referenced. Moreover,the server may receive encoded data from the terminals, change referencerelationship between items of data or correct or replace picturesthemselves, and then perform the encoding. This makes it possible togenerate a stream with increased quality and efficiency for theindividual items of data.

Moreover, the server may stream video data after performing transcodingto convert the encoding format of the video data. For example, theserver may convert the encoding format from MPEG to VP, and may convertH.264 to H.265.

In this way, encoding can be performed by a terminal or one or moreservers. Accordingly, although the device that performs the encoding isreferred to as a “server” or “terminal” in the following description,some or all of the processes performed by the server may be performed bythe terminal, and likewise some or all of the processes performed by theterminal may be performed by the server. This also applies to decodingprocesses.

[3D, Multi-Angle]

In recent years, usage of images or videos combined from images orvideos of different scenes concurrently captured or the same scenecaptured from different angles by a plurality of terminals such ascamera ex113 and/or smartphone ex115 has increased. Videos captured bythe terminals are combined based on, for example, theseparately-obtained relative positional relationship between theterminals, or regions in a video having matching feature points.

In addition to the encoding of two-dimensional moving pictures, theserver may encode a still image based on scene analysis of a movingpicture either automatically or at a point in time specified by theuser, and transmit the encoded still image to a reception terminal.Furthermore, when the server can obtain the relative positionalrelationship between the video capturing terminals, in addition totwo-dimensional moving pictures, the server can generatethree-dimensional geometry of a scene based on video of the same scenecaptured from different angles. Note that the server may separatelyencode three-dimensional data generated from, for example, a pointcloud, and may, based on a result of recognizing or tracking a person orobject using three-dimensional data, select or reconstruct and generatea video to be transmitted to a reception terminal from videos capturedby a plurality of terminals.

This allows the user to enjoy a scene by freely selecting videoscorresponding to the video capturing terminals, and allows the user toenjoy the content obtained by extracting, from three-dimensional datareconstructed from a plurality of images or videos, a video from aselected viewpoint. Furthermore, similar to with video, sound may berecorded from relatively different angles, and the server may multiplex,with the video, audio from a specific angle or space in accordance withthe video, and transmit the result.

In recent years, content that is a composite of the real world and avirtual world, such as virtual reality (VR) and augmented reality (AR)content, has also become popular. In the case of VR images, the servermay create images from the viewpoints of both the left and right eyesand perform encoding that tolerates reference between the two viewpointimages, such as multi-view coding (MVC), and, alternatively, may encodethe images as separate streams without referencing. When the images aredecoded as separate streams, the streams may be synchronized whenreproduced so as to recreate a virtual three-dimensional space inaccordance with the viewpoint of the user.

In the case of AR images, the server superimposes virtual objectinformation existing in a virtual space onto camera informationrepresenting a real-world space, based on a three-dimensional positionor movement from the perspective of the user. The decoder may obtain orstore virtual object information and three-dimensional data, generatetwo-dimensional images based on movement from the perspective of theuser, and then generate superimposed data by seamlessly connecting theimages. Alternatively, the decoder may transmit, to the server, motionfrom the perspective of the user in addition to a request for virtualobject information, and the server may generate superimposed data basedon three-dimensional data stored in the server in accordance with thereceived motion, and encode and stream the generated superimposed datato the decoder. Note that superimposed data includes, in addition to RGBvalues, an a value indicating transparency, and the server sets the αvalue for sections other than the object generated fromthree-dimensional data to, for example, 0, and may perform the encodingwhile those sections are transparent. Alternatively, the server may setthe background to a predetermined RGB value, such as a chroma key, andgenerate data in which areas other than the object are set as thebackground.

Decoding of similarly streamed data may be performed by the client(i.e., the terminals), on the server side, or divided therebetween. Inone example, one terminal may transmit a reception request to a server,the requested content may be received and decoded by another terminal,and a decoded signal may be transmitted to a device having a display. Itis possible to reproduce high image quality data by decentralizingprocessing and appropriately selecting content regardless of theprocessing ability of the communications terminal itself. In yet anotherexample, while a TV, for example, is receiving image data that is largein size, a region of a picture, such as a tile obtained by dividing thepicture, may be decoded and displayed on a personal terminal orterminals of a viewer or viewers of the TV. This makes it possible forthe viewers to share a big-picture view as well as for each viewer tocheck his or her assigned area or inspect a region in further detail upclose.

In the future, both indoors and outdoors, in situations in which aplurality of wireless connections are possible over near, mid, and fardistances, it is expected to be able to seamlessly receive content evenwhen switching to data appropriate for the current connection, using astreaming system standard such as MPEG-DASH. With this, the user canswitch between data in real time while freely selecting a decoder ordisplay apparatus including not only his or her own terminal, but also,for example, displays disposed indoors or outdoors. Moreover, based on,for example, information on the position of the user, decoding can beperformed while switching which terminal handles decoding and whichterminal handles the displaying of content. This makes it possible to,while in route to a destination, display, on the wall of a nearbybuilding in which a device capable of displaying content is embedded oron part of the ground, map information while on the move. Moreover, itis also possible to switch the bit rate of the received data based onthe accessibility to the encoded data on a network, such as when encodeddata is cached on a server quickly accessible from the receptionterminal or when encoded data is copied to an edge server in a contentdelivery service.

[Scalable Encoding]

The switching of content will be described with reference to a scalablestream, illustrated in FIG. 34 , that is compression coded viaimplementation of the moving picture encoding method described in theabove embodiments. The server may have a configuration in which contentis switched while making use of the temporal and/or spatial scalabilityof a stream, which is achieved by division into and encoding of layers,as illustrated in FIG. 34 . Note that there may be a plurality ofindividual streams that are of the same content but different quality.In other words, by determining which layer to decode up to based oninternal factors, such as the processing ability on the decoder side,and external factors, such as communication bandwidth, the decoder sidecan freely switch between low resolution content and high resolutioncontent while decoding. For example, in a case in which the user wantsto continue watching, at home on a device such as a TV connected to theinternet, a video that he or she had been previously watching onsmartphone ex115 while on the move, the device can simply decode thesame stream up to a different layer, which reduces server side load.

Furthermore, in addition to the configuration described above in whichscalability is achieved as a result of the pictures being encoded perlayer and the enhancement layer is above the base layer, the enhancementlayer may include metadata based on, for example, statisticalinformation on the image, and the decoder side may generate high imagequality content by performing super-resolution imaging on a picture inthe base layer based on the metadata. Super-resolution imaging may beimproving the SN ratio while maintaining resolution and/or increasingresolution. Metadata includes information for identifying a linear or anon-linear filter coefficient used in super-resolution processing, orinformation identifying a parameter value in filter processing, machinelearning, or least squares method used in super-resolution processing.

Alternatively, a configuration in which a picture is divided into, forexample, tiles in accordance with the meaning of, for example, an objectin the image, and on the decoder side, only a partial region is decodedby selecting a tile to decode, is also acceptable. Moreover, by storingan attribute about the object (person, car, ball, etc.) and a positionof the object in the video (coordinates in identical images) asmetadata, the decoder side can identify the position of a desired objectbased on the metadata and determine which tile or tiles include thatobject. For example, as illustrated in FIG. 35 , metadata is storedusing a data storage structure different from pixel data such as an SEImessage in HEVC. This metadata indicates, for example, the position,size, or color of the main object.

Moreover, metadata may be stored in units of a plurality of pictures,such as stream, sequence, or random access units. With this, the decoderside can obtain, for example, the time at which a specific personappears in the video, and by fitting that with picture unit information,can identify a picture in which the object is present and the positionof the object in the picture.

[Web Page Optimization]

FIG. 36 illustrates an example of a display screen of a web page on, forexample, computer ex111. FIG. 37 illustrates an example of a displayscreen of a web page on, for example, smartphone ex115. As illustratedin FIG. 36 and FIG. 37 , a web page may include a plurality of imagelinks which are links to image content, and the appearance of the webpage differs depending on the device used to view the web page. When aplurality of image links are viewable on the screen, until the userexplicitly selects an image link, or until the image link is in theapproximate center of the screen or the entire image link fits in thescreen, the display apparatus (decoder) displays, as the image links,still images included in the content or I pictures, displays video suchas an animated gif using a plurality of still images or I pictures, forexample, or receives only the base layer and decodes and displays thevideo.

When an image link is selected by the user, the display apparatusdecodes giving the highest priority to the base layer. Note that ifthere is information in the HTML code of the web page indicating thatthe content is scalable, the display apparatus may decode up to theenhancement layer. Moreover, in order to guarantee real timereproduction, before a selection is made or when the bandwidth isseverely limited, the display apparatus can reduce delay between thepoint in time at which the leading picture is decoded and the point intime at which the decoded picture is displayed (that is, the delaybetween the start of the decoding of the content to the displaying ofthe content) by decoding and displaying only forward reference pictures(I picture, P picture, forward reference B picture). Moreover, thedisplay apparatus may purposely ignore the reference relationshipbetween pictures and coarsely decode all B and P pictures as forwardreference pictures, and then perform normal decoding as the number ofpictures received over time increases.

[Autonomous Driving]

When transmitting and receiving still image or video data such two- orthree-dimensional map information for autonomous driving or assisteddriving of an automobile, the reception terminal may receive, inaddition to image data belonging to one or more layers, information on,for example, the weather or road construction as metadata, and associatethe metadata with the image data upon decoding. Note that metadata maybe assigned per layer and, alternatively, may simply be multiplexed withthe image data.

In such a case, since the automobile, drone, airplane, etc., includingthe reception terminal is mobile, the reception terminal can seamlesslyreceive and decode while switching between base stations among basestations ex106 through ex110 by transmitting information indicating theposition of the reception terminal upon reception request. Moreover, inaccordance with the selection made by the user, the situation of theuser, or the bandwidth of the connection, the reception terminal candynamically select to what extent the metadata is received or to whatextent the map information, for example, is updated.

With this, in content providing system ex100, the client can receive,decode, and reproduce, in real time, encoded information transmitted bythe user.

[Streaming of Individual Content]

In content providing system ex100, in addition to high image quality,long content distributed by a video distribution entity, unicast ormulticast streaming of low image quality, short content from anindividual is also possible. Moreover, such content from individuals islikely to further increase in popularity. The server may first performediting processing on the content before the encoding processing inorder to refine the individual content. This may be achieved with, forexample, the following configuration.

In real-time while capturing video or image content or after the contenthas been captured and accumulated, the server performs recognitionprocessing based on the raw or encoded data, such as capture errorprocessing, scene search processing, meaning analysis, and/or objectdetection processing. Then, based on the result of the recognitionprocessing, the server-either when prompted or automatically-edits thecontent, examples of which include: correction such as focus and/ormotion blur correction; removing low-priority scenes such as scenes thatare low in brightness compared to other pictures or out of focus; objectedge adjustment; and color tone adjustment. The server encodes theedited data based on the result of the editing. It is known thatexcessively long videos tend to receive fewer views. Accordingly, inorder to keep the content within a specific length that scales with thelength of the original video, the server may, in addition to thelow-priority scenes described above, automatically clip out scenes withlow movement based on an image processing result. Alternatively, theserver may generate and encode a video digest based on a result of ananalysis of the meaning of a scene.

Note that there are instances in which individual content may includecontent that infringes a copyright, moral right, portrait rights, etc.Such an instance may lead to an unfavorable situation for the creator,such as when content is shared beyond the scope intended by the creator.Accordingly, before encoding, the server may, for example, edit imagesso as to blur faces of people in the periphery of the screen or blur theinside of a house, for example. Moreover, the server may be configuredto recognize the faces of people other than a registered person inimages to be encoded, and when such faces appear in an image, forexample, apply a mosaic filter to the face of the person. Alternatively,as pre- or post-processing for encoding, the user may specify, forcopyright reasons, a region of an image including a person or a regionof the background be processed, and the server may process the specifiedregion by, for example, replacing the region with a different image orblurring the region. If the region includes a person, the person may betracked in the moving picture the head region may be replaced withanother image as the person moves.

Moreover, since there is a demand for real-time viewing of contentproduced by individuals, which tends to be small in data size, thedecoder first receives the base layer as the highest priority andperforms decoding and reproduction, although this may differ dependingon bandwidth. When the content is reproduced two or more times, such aswhen the decoder receives the enhancement layer during decoding andreproduction of the base layer and loops the reproduction, the decodermay reproduce a high image quality video including the enhancementlayer. If the stream is encoded using such scalable encoding, the videomay be low quality when in an unselected state or at the start of thevideo, but it can offer an experience in which the image quality of thestream progressively increases in an intelligent manner. This is notlimited to just scalable encoding; the same experience can be offered byconfiguring a single stream from a low quality stream reproduced for thefirst time and a second stream encoded using the first stream as areference.

Other Usage Examples

The encoding and decoding may be performed by LSI ex500, which istypically included in each terminal. LSI ex500 may be configured of asingle chip or a plurality of chips. Software for encoding and decodingmoving pictures may be integrated into some type of a recording medium(such as a CD-ROM, a flexible disk, or a hard disk) that is readable by,for example, computer ex111, and the encoding and decoding may beperformed using the software. Furthermore, when smartphone ex115 isequipped with a camera, the video data obtained by the camera may betransmitted. In this case, the video data is encoded by LSI ex500included in smartphone ex115.

Note that LSI ex500 may be configured to download and activate anapplication. In such a case, the terminal first determines whether it iscompatible with the scheme used to encode the content or whether it iscapable of executing a specific service. When the terminal is notcompatible with the encoding scheme of the content or when the terminalis not capable of executing a specific service, the terminal firstdownloads a codec or application software then obtains and reproducesthe content.

Aside from the example of content providing system ex100 that usesinternet ex101, at least the moving picture encoder (image encoder) orthe moving picture decoder (image decoder) described in the aboveembodiments may be implemented in a digital broadcasting system. Thesame encoding processing and decoding processing may be applied totransmit and receive broadcast radio waves superimposed with multiplexedaudio and video data using, for example, a satellite, even though thisis geared toward multicast whereas unicast is easier with contentproviding system ex100.

[Hardware Configuration]

FIG. 38 illustrates smartphone ex115. FIG. 39 illustrates aconfiguration example of smartphone ex115. Smartphone ex115 includesantenna ex450 for transmitting and receiving radio waves to and frombase station ex110, camera ex465 capable of capturing video and stillimages, and display ex458 that displays decoded data, such as videocaptured by camera ex465 and video received by antenna ex450. Smartphoneex115 further includes user interface ex466 such as a touch panel, audiooutput unit ex457 such as a speaker for outputting speech or otheraudio, audio input unit ex456 such as a microphone for audio input,memory ex467 capable of storing decoded data such as captured video orstill images, recorded audio, received video or still images, and mail,as well as decoded data, and slot ex464 which is an interface for SIMex468 for authorizing access to a network and various data. Note thatexternal memory may be used instead of memory ex467.

Moreover, main controller ex460 which comprehensively controls displayex458 and user interface ex466, power supply circuit ex461, userinterface input controller ex462, video signal processor ex455, camerainterface ex463, display controller ex459, modulator/demodulator ex452,multiplexer/demultiplexer ex453, audio signal processor ex454, slotex464, and memory ex467 are connected via bus ex470.

When the user turns the power button of power supply circuit ex461 on,smartphone ex115 is powered on into an operable state by each componentbeing supplied with power from a battery pack.

Smartphone ex115 performs processing for, for example, calling and datatransmission, based on control performed by main controller ex460, whichincludes a CPU, ROM, and RAM. When making calls, an audio signalrecorded by audio input unit ex456 is converted into a digital audiosignal by audio signal processor ex454, and this is applied with spreadspectrum processing by modulator/demodulator ex452 and digital-analogconversion and frequency conversion processing by transmitter/receiverex451, and then transmitted via antenna ex450. The received data isamplified, frequency converted, and analog-digital converted, inversespread spectrum processed by modulator/demodulator ex452, converted intoan analog audio signal by audio signal processor ex454, and then outputfrom audio output unit ex457. In data transmission mode, text,still-image, or video data is transmitted by main controller ex460 viauser interface input controller ex462 as a result of operation of, forexample, user interface ex466 of the main body, and similar transmissionand reception processing is performed. In data transmission mode, whensending a video, still image, or video and audio, video signal processorex455 compression encodes, via the moving picture encoding methoddescribed in the above embodiments, a video signal stored in memoryex467 or a video signal input from camera ex465, and transmits theencoded video data to multiplexer/demultiplexer ex453. Moreover, audiosignal processor ex454 encodes an audio signal recorded by audio inputunit ex456 while camera ex465 is capturing, for example, a video orstill image, and transmits the encoded audio data tomultiplexer/demultiplexer ex453. Multiplexer/demultiplexer ex453multiplexes the encoded video data and encoded audio data using apredetermined scheme, modulates and converts the data usingmodulator/demodulator (modulator/demodulator circuit) ex452 andtransmitter/receiver ex451, and transmits the result via antenna ex450.

When video appended in an email or a chat, or a video linked from a webpage, for example, is received, in order to decode the multiplexed datareceived via antenna ex450, multiplexer/demultiplexer ex453demultiplexes the multiplexed data to divide the multiplexed data into abitstream of video data and a bitstream of audio data, supplies theencoded video data to video signal processor ex455 via synchronous busex470, and supplies the encoded audio data to audio signal processorex454 via synchronous bus ex470. Video signal processor ex455 decodesthe video signal using a moving picture decoding method corresponding tothe moving picture encoding method described in the above embodiments,and video or a still image included in the linked moving picture file isdisplayed on display ex458 via display controller ex459. Moreover, audiosignal processor ex454 decodes the audio signal and outputs audio fromaudio output unit ex457. Note that since real-time streaming is becomingmore and more popular, there are instances in which reproduction of theaudio may be socially inappropriate depending on the user's environment.Accordingly, as an initial value, a configuration in which only videodata is reproduced, i.e., the audio signal is not reproduced, ispreferable. Audio may be synchronized and reproduced only when an input,such as when the user clicks video data, is received.

Although smartphone ex115 was used in the above example, threeimplementations are conceivable: a transceiver terminal including bothan encoder and a decoder; a transmitter terminal including only anencoder; and a receiver terminal including only a decoder. Further, inthe description of the digital broadcasting system, an example is givenin which multiplexed data obtained as a result of video data beingmultiplexed with, for example, audio data, is received or transmitted,but the multiplexed data may be video data multiplexed with data otherthan audio data, such as text data related to the video. Moreover, thevideo data itself rather than multiplexed data maybe received ortransmitted.

Although main controller ex460 including a CPU is described ascontrolling the encoding or decoding processes, terminals often includeGPUs. Accordingly, a configuration is acceptable in which a large areais processed at once by making use of the performance ability of the GPUvia memory shared by the CPU and GPU or memory including an address thatis managed so as to allow common usage by the CPU and GPU. This makes itpossible to shorten encoding time, maintain the real-time nature of thestream, and reduce delay. In particular, processing relating to motionestimation, deblocking filtering, sample adaptive offset (SAO), andtransformation/quantization can be effectively carried out by the GPUinstead of the CPU in units of, for example pictures, all at once.

An encoder according to an embodiment of the present disclosure may bean encoder that encodes a picture and includes a processor and memory.The processor may include: a block partition determiner that partitionsthe picture into a plurality of blocks, using a set of block partitionmodes obtained by combining one or more block partition modes each ofwhich defines a partition type, the picture being read from the memory;and an encoding unit that encodes the plurality of blocks. The set ofblock partition modes may include a first partition mode that defines apartition direction and a total number of partitions for partitioning afirst block, and a second block partition mode that defines a partitiondirection and a total number of partitions for partitioning a secondblock which is one of blocks obtained after the first block ispartitioned. When the total number of partitions of the first blockpartition mode is three, the second block is a center block among theblocks obtained after the first block is partitioned, and the partitiondirection of the second block partition mode is same as the partitiondirection of the first block partition mode, the second block partitionmode may include only a block partition mode indicating that the totalnumber of partitions is three.

A parameter for identifying the second block partition mode in theencoder according an embodiment of the present disclosure a may includea first flag that indicates whether a block is to be partitionedhorizontally or vertically, and need not include a second flagindicating a total number of partitions into which the block is to bepartitioned.

An encoder according to an embodiment of the present disclosure may bean encoder that encodes a picture and includes a processor and memory.The processor may include: a block partition determiner that partitionsthe picture into a plurality of blocks, using a set of block partitionmodes obtained by combining one or more block partition modes each ofwhich defines a partition type, the picture being read from the memory;and an encoding unit that encodes the plurality of blocks. The set ofblock partition modes may include a first partition mode that defines apartition direction and a total number of partitions for partitioning afirst block, and a second block partition mode that defines a partitiondirection and a total number of partitions for partitioning a secondblock which is one of blocks obtained after the first block ispartitioned. When the total number of partitions of the first blockpartition mode is three, the second block is a center block among theblocks obtained after the first block is partitioned, and the partitiondirection of the second block partition mode is same as the partitiondirection of the first block partition mode, the second block partitionmode indicating that the total number of partitions is two need not beused.

An encoder according to an embodiment of the present disclosure may bean encoder that encodes a picture, and includes: a processor and amemory. The processor may include: a block partition determiner thatpartitions the picture into a plurality of blocks, using a set of blockpartition modes obtained by combining one or more block partition modeseach of which defines a partition type, the picture being read from thememory; and an encoding unit that encodes the plurality of blocks. Theset of block partition modes may include a first partition mode and asecond block partition mode each defining a partition direction and atotal number of partitions. The block partition determiner may restrictuse of the second block partition mode which indicates that the numberof partitions is two.

A parameter for identifying the second block partition mode in theencoder according to an embodiment of the present disclosure, mayinclude a first flag that indicates whether the block is to bepartitioned horizontally or vertically, and a second flag indicatingwhether the block is to be partitioned into two or more.

The parameter in the encoder according to an embodiment of the presentdisclosure may be provided in slice data.

An encoder according to an embodiment of the present disclosure may bean encoder that encodes a picture, and includes: a processor; and amemory. The processor may include: a block partition determiner thatpartitions the picture into a set of blocks including a plurality ofblocks, using a set of block partition modes obtained by combining oneor more block partition modes each of which defines a partition type,the picture being read from the memory; and an encoding unit thatencodes the plurality of blocks. When a first set of blocks obtained byusing a first set of block partition modes and a second set of blocksobtained by using a second set of block partition modes are the same,the block partition determiner may perform partitioning using only oneof the first block partition mode or the second block partition mode.

The block partition determiner in the encoder according to an embodimentof the present disclosure may, based on a first amount of code of thefirst set of block partition modes and a second amount of codes of thesecond set of block partition modes, perform partitioning using the setof block partition modes of the lesser one of the first amount of codesand the second amount of codes.

The block partition determiner in the encoder according to an embodimentof the present disclosure may, based on a first amount of code of thefirst set of block partition modes and a second amount of codes of thesecond set of block partition modes, perform partitioning using the setof block partition modes that appears first in a predetermined orderamong the first set of block partition modes and the second set of blockpartition modes, when the first amount of code and the second amount ofcode are equal.

A decoder according to an embodiment of the present disclosure may be adecoder that decodes an encoded signal and includes a processor andmemory. The processor may includes a block partition determiner thatpartitions the encoded signal into a plurality of blocks, using a set ofblock partition modes obtained by combining one or more block partitionmodes each of which defines a partition type, the encoded signal beingread from the memory; and a decoding unit that decodes the plurality ofblocks. The set of block partition modes may include a first partitionmode that defines a partition direction and a total number of partitionsfor partitioning a first block, and a second block partition mode thatdefines a partition direction and a total number of partitions forpartitioning a second block which is one of blocks obtained after thefirst block is partitioned. When the total number of partitions of thefirst block partition mode is three, the second block is a center blockamong the blocks obtained after the first block is partitioned, and thepartition direction of the second block partition mode is same as thepartition direction of the first block partition mode, the second blockpartition mode may include only a block partition mode indicating thatthe total number of partitions is three.

A parameter for identifying the second block partition mode in thedecoder according to an embodiment of the present disclosure may includea first flag that indicates whether a block is to be partitionedhorizontally or vertically, and need not include a second flagindicating a total number of partitions into which the block is to bepartitioned.

A decoder according to an embodiment of the present disclosure may be adecoder that decodes an encoded signal and includes a processor andmemory. The processor may includes a block partition determiner thatpartitions the encoded signal into a plurality of blocks, using a set ofblock partition modes obtained by combining one or more block partitionmodes each of which defines a partition type, the encoded signal beingread from the memory; and a decoding unit that decodes the plurality ofblocks. The set of block partition modes may include a first partitionmode that defines a partition direction and a total number of partitionsfor partitioning a first block, and a second block partition mode thatdefines a partition direction and a total number of partitions forpartitioning a second block which is one of blocks obtained after thefirst block is partitioned. When the total number of partitions of thefirst block partition mode is three, the second block is a center blockamong the blocks obtained after the first block is partitioned, and thepartition direction of the second block partition mode is same as thepartition direction of the first block partition mode, the second blockpartition mode indicating that the total number of partitions is twoneed not be used.

A decoder according to an embodiment of the present disclosure may be adecoder that decodes an encoded signal, and includes a processor and amemory. The processor may include: a block partition determiner thatpartitions the encoded signal into a plurality of blocks, using a set ofblock partition modes obtained by combining one or more block partitionmodes each of which defines a partition type, the encoded signal beingread from the memory; and a decoding unit that decodes the plurality ofblocks. The set of block partition modes may include a first blockpartition mode and a second block partition mode each defining apartition direction and the number of partitions. The block partitiondeterminer may restrict use of the second block partition mode whichindicates that the number of partitions is two.

A parameter for identifying the second block partition mode in thedecoder according to an embodiment of the present disclosure may includea first flag that indicates whether a block is to be partitionedhorizontally or vertically, and a second flag indicating whether theblock is to be partitioned into two or more.

The parameter in the decoder according to an embodiment of the presentdisclosure may be provided in slice data.

A decoder according to an embodiment of the present disclosure may be adecoder that decodes an encoded signal, and includes: a processor; and amemory. The processor may include: a block partition determiner thatpartitions the encoded signal into a set of blocks including a pluralityof blocks, using a set of block partition modes obtained by combiningone or more block partition modes each of which defines a partitiontype, the encoded signal being read from the memory; and a decoding unitthat decodes the plurality of blocks. When a first set of blocksobtained by using a first set of block partition modes and a second setof blocks obtained by using a second set of block partition modes arethe same, the block partition determiner may perform partitioning usingonly one of the first block partition mode or the second block partitionmode.

The block partition determiner in the decoder according to an embodimentof the present disclosure may, based on a first amount of code of thefirst set of block partition modes and a second amount of codes of thesecond set of block partition modes, perform partitioning using the setof block partition modes of the lesser one of the first amount of codesand the second amount of codes.

The block partition determiner in the decoder according to an embodimentof the present disclosure may, based on a first amount of code of thefirst set of block partition modes and a second amount of codes of thesecond set of block partition modes, perform partitioning using the setof block partition modes that appears first in a predetermined orderamong the first set of block partition modes and the second set of blockpartition modes, when the first amount of code and the second amount ofcode are equal.

An encoding method according to an embodiment of the present disclosuremay include: partitioning a picture into a plurality of blocks, using aset of block partition modes obtained by combining one or more blockpartition modes each of which defines a partition type, the picturebeing read from a memory; and encoding the plurality of blocks. The setof block partition modes may include a first partition mode that definesa partition direction and a total number of partitions for partitioninga first block, and a second block partition mode that defines apartition direction and a total number of partitions for partitioning asecond block which is one of blocks obtained after the first block ispartitioned. In the partitioning, when the total number of partitions ofthe first block partition mode is three, the second block is a centerblock among the blocks obtained after the first block is partitioned,and the partition direction of the second block partition mode is sameas the partition direction of the first block partition mode, the secondblock partition mode may include only a block partition mode indicatingthat the total number of partitions is three.

A parameter for identifying the second block partition mode in theencoding method according to an embodiment of the present disclosure mayinclude a first flag that indicates whether a block is to be partitionedhorizontally or vertically, and need not include a second flagindicating a total number of partitions into which the block is to bepartitioned.

An encoding method according to an embodiment of the present disclosuremay include: partitioning a picture into a plurality of blocks, using aset of block partition modes obtained by combining one or more blockpartition modes each of which defines a partition type, the picturebeing read from the memory; and encoding the plurality of blocks. Theset of block partition modes may include a first partition mode thatdefines a partition direction and a total number of partitions forpartitioning a first block, and a second block partition mode thatdefines a partition direction and a total number of partitions forpartitioning a second block which is one of blocks obtained after thefirst block is partitioned. In the partitioning, when the total numberof partitions of the first block partition mode is three, the secondblock is a center block among the blocks obtained after the first blockis partitioned, and the partition direction of the second blockpartition mode is same as the partition direction of the first blockpartition mode, the second block partition mode indicating that thetotal number of partitions is two need not be used.

An encoding method according to an embodiment of the present disclosuremay include: partitioning a picture into a plurality of blocks, using aset of block partition modes obtained by combining one or more blockpartition modes each of which defines a partition type, the picturebeing read from the memory; and encoding the plurality of blocks. Theset of block partition modes may include a first block partition modeand a second block partition mode each defining a partition directionand the number of partitions. In the partitioning, use of the secondblock partition mode which indicates that the number of partitions istwo may be restricted.

A parameter for identifying the second block partition mode in theencoding method according to an embodiment of the present disclosure mayinclude a first flag that indicates whether a block is to be partitionedhorizontally or vertically, and a second flag indicating whether theblock is to be partitioned into two or more.

The parameter in the encoding method according to an embodiment of thepresent disclosure may be provided in slice data.

An encoding method according to an embodiment of the present disclosuremay include: partitioning a picture into a set of blocks including aplurality of blocks, using a set of block partition modes obtained bycombining one or more block partition modes each of which defines apartition type, the picture being read from the memory; and encoding theplurality of blocks. In the partitioning, when a first set of blocksobtained by using a first set of block partition modes and a second setof blocks obtained by using a second set of block partition modes arethe same, the partitioning may be performed using only one of the firstblock partition mode or the second block partition mode.

The partitioning in the encoding method according to an embodiment ofthe present disclosure may, based on a first amount of code of the firstset of block partition modes and a second amount of codes of the secondset of block partition modes, be performed using the set of blockpartition modes of the lesser one of the first amount of codes and thesecond amount of codes.

The partitioning in the encoding method according to an embodiment ofthe present disclosure may, based on a first amount of code of the firstset of block partition modes and a second amount of codes of the secondset of block partition modes, be performed using the set of blockpartition modes that appears first in a predetermined order among thefirst set of block partition modes and the second set of block partitionmodes, when the first amount of code and the second amount of code areequal.

A decoding method according to an embodiment of the present disclosuremay include: partitioning an encoded signal into a plurality of blocks,using a set of block partition modes obtained by combining one or moreblock partition modes each of which defines a partition type, theencoded signal being read from a memory; and decoding the plurality ofblocks. The set of block partition modes may include a first partitionmode that defines a partition direction and a total number of partitionsfor partitioning a first block, and a second block partition mode thatdefines a partition direction and a total number of partitions forpartitioning a second block which is one of blocks obtained after thefirst block is partitioned. In the partitioning, when the total numberof partitions of the first block partition mode is three, the secondblock is a center block among the blocks obtained after the first blockis partitioned, and the partition direction of the second blockpartition mode is same as the partition direction of the first blockpartition mode, the second block partition mode may include only a blockpartition mode indicating that the total number of partitions is three.

A parameter for identifying the second block partition mode in thedecoding method according to an embodiment of the present disclosure mayinclude a first flag that indicates whether a block is to be partitionedhorizontally or vertically, and a second flag indicating whether theblock is to be partitioned into two or more.

A decoding method according to an embodiment of the present disclosuremay include: partitioning an encoded signal into a plurality of blocks,using a set of block partition modes obtained by combining one or moreblock partition modes each of which defines a partition type, theencoded signal being read from the memory; and decoding the plurality ofblocks. The set of block partition modes may include a first partitionmode that defines a partition direction and a total number of partitionsfor partitioning a first block, and a second block partition mode thatdefines a partition direction and a total number of partitions forpartitioning a second block which is one of blocks obtained after thefirst block is partitioned. In the partitioning, when the total numberof partitions of the first block partition mode is three, the secondblock is a center block among the blocks obtained after the first blockis partitioned, and the partition direction of the second blockpartition mode is same as the partition direction of the first blockpartition mode, the second block partition mode indicating that thetotal number of partitions is two need not be used.

A decoding method according to an embodiment of the present disclosuremay include: partitioning an encoded signal into a plurality of blocks,using a set of block partition modes obtained by combining one or moreblock partition modes each of which defines a partition type, theencoded signal being read from the memory; and decoding the plurality ofblocks. The set of block partition modes may include a first blockpartition mode and a second block partition mode each defining apartition direction and the number of partitions. In the partitioning,use of the second block partition mode which indicates that the numberof partitions is two may be restricted.

A decoding method according to an embodiment of the present disclosuremay include: partitioning an encoded signal into a set of blocksincluding a plurality of blocks, using a set of block partition modesobtained by combining one or more block partition modes each of whichdefines a partition type, the encoded signal being read from the memory;and decoding the plurality of blocks. In the partitioning, when a firstset of blocks obtained by using a first set of block partition modes anda second set of blocks obtained by using a second set of block partitionmodes are the same, partitioning may be performed using only one of thefirst block partition mode or the second block partition mode.

A recording medium according to an embodiment of the present disclosureis a non-transitory computer-readable recording medium for use in acomputer, the recording medium having a computer program recordedthereon which may cause the computer to execute: partitioning a pictureinto a plurality of blocks, using a set of block partition modesobtained by combining one or more block partition modes each of whichdefines a partition type, the picture being read from a memory; anddecoding the plurality of blocks. The set of block partition modes mayinclude a first partition mode that defines a partition direction and atotal number of partitions for partitioning a first block, and a secondblock partition mode that defines a partition direction and a totalnumber of partitions for partitioning a second block which is one ofblocks obtained after the first block is partitioned. In thepartitioning, when the total number of partitions of the first blockpartition mode is three, the second block is a center block among theblocks obtained after the first block is partitioned, and the partitiondirection of the second block partition mode is same as the partitiondirection of the first block partition mode, the second block partitionmode may include only a block partition mode indicating that the totalnumber of partitions is three.

A recording medium according to an embodiment of the present disclosureis a non-transitory computer-readable recording medium for use in acomputer, the recording medium having a computer program recordedthereon which may cause the computer to execute: partitioning a pictureinto a plurality of blocks, using a set of block partition modesobtained by combining one or more block partition modes each of whichdefines a partition type, the picture being read from a memory; anddecoding the plurality of blocks. The set of block partition modes mayinclude a first partition mode that defines a partition direction and atotal number of partitions for partitioning a first block, and a secondblock partition mode that defines a partition direction and a totalnumber of partitions for partitioning a second block which is one ofblocks obtained after the first block is partitioned. In thepartitioning, when the total number of partitions of the first blockpartition mode is three, the second block is a center block among theblocks obtained after the first block is partitioned, and the partitiondirection of the second block partition mode is same as the partitiondirection of the first block partition mode, the second block partitionmode indicating that the total number of partitions is two need not beused.

A recording medium according to an embodiment of the present disclosureis a non-transitory computer-readable recording medium for use in acomputer, the recording medium having a computer program recordedthereon which may cause the computer to execute: partitioning a pictureinto a plurality of blocks, using a set of block partition modesobtained by combining one or more block partition modes each of whichdefines a partition type, the picture being read from the memory; andencoding the plurality of blocks. The set of block partition modes mayinclude a first block partition mode and a second block partition modeeach defining a partition direction and the number of partitions. In thepartitioning, use of the second block partition mode which indicatesthat the number of partitions is two may be restricted.

A recording medium according to an embodiment of the present disclosureis a non-transitory computer-readable recording medium for use in acomputer, the recording medium having a computer program recordedthereon which may cause the computer to execute: partitioning a pictureinto a set of blocks including a plurality of blocks, using a set ofblock partition modes obtained by combining one or more block partitionmodes each of which defines a partition type, the picture being readfrom the memory; and encoding the plurality of blocks. In thepartitioning, when a first set of blocks obtained by using a first setof block partition modes and a second set of blocks obtained by using asecond set of block partition modes are the same, partitioning may beperformed using only one of the first block partition mode or the secondblock partition mode.

Although only some exemplary embodiments of the present disclosure havebeen described in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of the present disclosure. Accordingly, all suchmodifications are intended to be included within the scope of thepresent disclosure.

INDUSTRIAL APPLICABILITY

The present disclosure can be used in multimedia encoding/decoding, andparticularly in an image and video encoder/decoder which uses blockencoding/decoding.

What is claimed is:
 1. An encoder that encodes a picture, the encodercomprising: circuitry; and memory, wherein using the memory, thecircuitry: partitions the picture into a plurality of blocks, using aset of block partition modes obtained by combining one or more blockpartition modes each of which defines a partition type, the picturebeing read from the memory; and encodes the plurality of blocks, the setof block partition modes includes a first block partition mode thatdefines a partition direction and a total number of partitions forpartitioning a first block, and a second block partition mode thatdefines a partition direction and a total number of partitions forpartitioning a second block which is one of blocks obtained after thefirst block is partitioned, in a case where the total number ofpartitions of the first block partition mode is three, the second blockis a center block among the blocks obtained after the first block ispartitioned, and the partition direction of the second block partitionmode is same as the partition direction of the first block partitionmode, the second block partition mode includes a block partition modeindicating that the total number of partitions is three, and a parameterfor identifying the second block partition mode includes a first flagindicating whether a block is to be partitioned horizontally orvertically, and does not include a second flag indicating a total numberof partitions into which the block is to be partitioned.
 2. An encodingmethod, comprising: partitioning a picture into a plurality of blocks,using a set of block partition modes obtained by combining one or moreblock partition modes each of which defines a partition type, thepicture being read from a memory; and encoding the plurality of blocks,wherein the set of block partition modes includes a first blockpartition mode that defines a partition direction and a total number ofpartitions for partitioning a first block, and a second block partitionmode that defines a partition direction and a total number of partitionsfor partitioning a second block which is one of blocks obtained afterthe first block is partitioned, in the partitioning, in a case where thetotal number of partitions of the first block partition mode is three,the second block is a center block among the blocks obtained after thefirst block is partitioned, and the partition direction of the secondblock partition mode is same as the partition direction of the firstblock partition mode, the second block partition mode includes a blockpartition mode indicating that the total number of partitions is three,and a parameter for identifying the second block partition mode includesa first flag indicating whether a block is to be partitionedhorizontally or vertically, and does not include a second flagindicating a total number of partitions into which the block is to bepartitioned.
 3. A non-transitory computer-readable recording mediumstoring a bitstream, the bitstream including an encoded signal andsyntax information according to which a decoder performs: partitioning apicture into a plurality of blocks, using a set of block partition modesobtained by combining one or more block partition modes each of whichdefines a partition type, the picture being read from a memory; anddecoding the plurality of blocks, wherein the set of block partitionmodes includes a first block partition mode that defines a partitiondirection and a total number of partitions for partitioning a firstblock, and a second block partition mode that defines a partitiondirection and a total number of partitions for partitioning a secondblock which is one of blocks obtained after the first block ispartitioned, in the partitioning, in a case where the total number ofpartitions of the first block partition mode is three, the second blockis a center block among the blocks obtained after the first block ispartitioned, and the partition direction of the second block partitionmode is same as the partition direction of the first block partitionmode, the second block partition mode includes a block partition modeindicating that the total number of partitions is three, and a parameterfor identifying the second block partition mode includes a first flagindicating whether a block is to be partitioned horizontally orvertically, and does not include a second flag indicating a total numberof partitions into which the block is to be partitioned.